7

AMERICAN

JOURNAL OF BOTANY

OFFICIAL PUBLICATION OF THE BOTANICAL SOCIETY OF AMERICA

EDITORIAL COMMITTEE

F. C. Newcombe, Editor-in-Chief,

University of Michigan

C. Stuart Gager, Business Manager A. S. Hitchcock,

Brooklyn Botanic Garden Bureau of Plant Industry

Irving W. Bailey, L. R. Jones,

Bussey Institution U.niversity of Wisconsin

H. H. Bartlett, Edgar W. Olive,

University of Michigan Brooklyn Botanic Garden

VOLUME II 1915

WITH EIGHTEEN PLATES AND NINETY TEXT FIGURES

PUBLISHED

IN COOPERATION WITH THE BOTANICAL SOCIETY OF AMERICA

BY THE

BROOKLYN BOTANIC GARDEN At 41 North Queen Street, Lancaster, Pa.

PRESS OF

The New era Printing Company Lancaster. Pa.

TABLE OF CONTENTS, VOLUME II, 1915

No. I, January

PAGE

/ Investigations on the phylogeny of the Angiosperms. 5. Foliar evidence as to the ancestry and early climatic environment of the Angiosperms (with plates I-IV).

Edmund W. Sinnott and Irving W. Bailey i The growth-forms of the flora of New York and vicinity.

Norman Taylor 23 / The temperature of leaves of Pinus in winter (with four text

figures) John H. Ehlers 32

No. 2, February

Some effects of the brown-rot fungus upon the composition of

the peach LoN A. Hawkins 71

Negative heliotropism of urediniospore germ tubes (with two

text figures) F. D. Fromme 82

A woody stem in Merremia gemella induced by high warm water

(with two text figures) Frank C. Gates 86

Picro-nigrosin, a combination fixative and stain for algae.

Otis F. Curtis and Reginald H. Colley 89

Normal and abnormal permeability W. J. V. Osterhout 93

A simplified precision auxanometer (with three text figures).

W. T. BoviE 95 The mutations of Oenothera stenomercs (with four text figures).

H. H. Bartlett 100

No. 3, March

Morphology as a factor in determining relationships.

J. M. Greenman III

The genetic relationship of parasites Frank Dunn Kern 116

The experimental study of genetic relationships.

H. H. Bartlett 132

iii

TABLE OF CONTENTS

No. 4, April

A three-salt nutrient solution for plants John W. Shtve 157

Preliminary note on the morphology of Gnetum.

W. P. Thompson 161 The persistence of viable pycnospores of the chestnut blight fungus on normal bark below lesions.

R. A. Studhalter and F. D. Heald 162 A taxonomic study of Setaria italica and its immediate allies.

F. Tracy Hubbard 169

No. 5, May

The morphology and systematic position of Podomitrium (with

seven text figures) Douglas Houghton Campbell 199

On the relation of root growth and development to the temperature and aeration of the soil (with five text figures).

W. A. Cannon 211 The anatomy of a hybrid Equisetum (with plates V-VHI).

Ruth Holden 225 Some features in the anatomy of the Malvales (with plates

IX-XI) C. C. FoRSAiTH 238

The absorption of ions by living and dead roots.

H. V. Johnson 250

No. 6, June

The exchange of ions between the roots of Lupinus albus and culture solutions containing one nutrient salt (with thirteen text figures).

Rodney H. True and Harley Harris Bartlett 255 Notes on the forms of Castela Galapageia (with ten text figures).

Alb AN Stewart 279 The development of Pyronema confluens var. inigneum.

William H. Brown 289 New or noteworthy grasses A. S. Hitchcock 299

No. 7, July

The exchange of ions between the roots of Lupinus albus and culture solutions containing two nutrient salts (with three text figures).

Rodney H. True and Harley Harris Bartlett 311

TABLE OF CONTENTS

V

The probable non-validity of the genera Botryodiplodia, Diplodi- ella, Chaetodiplodia, and Lasiodiplodia (with plates XII- XIV) J. J. Taubenhaus 324

Factors influencing flower size in Nicotiana with special reference to questions of inheritance (with four text figures).

T. H. GooDSPEED AND R. E. Clausen 332

No. 8, October

The utilization of certain pentoses and compounds of pentoses by

Glomerella cingulata LoN A. Hawkins 375

The question of the toxicity of distilled water. . .R. P. Hibbard 389

An anatomical study of Gymnosporangium galls (with one text

figure, and plates XV and XVI) Alban Stewart 402

An extension to 5.99° of tables to determine the osmotic pressure of expressed vegetable saps from the depression of the freezing point J. Arthur Harris 418

Calcium hypochlorite as a seed sterilizer. . . .James K. Wilson 420

No. 9, November

Seasonal duration of ascospore expulsion of Endothia parasitica

(with six text figures). . . F. D. Heald and R. A. Studhalter 429 Dimorphism in Coniothyrium pirinum Sheldon (with fifteen text

figures) C. H. Crabill 449

The genus Espeletia (with six text figures and plate XVII)

Paul C. Standley 468 A study of the relation of transpiration to the size and number of stomata (with one text figure) .

Walter L. C. Muenscher 486

No. 10, December

A brief sketch of the life and work of Charles Edwin Bessey (with

plate XVIII) Raymond J. Pool 505

Heredity and mutation as cell phenomena . . . R. Ruggles Gates 5ig

The relation between vegetative vigor and reproduction in some

Saprolegniaceac (with two text figurCvs) . .Adrian J. Pieters 529

Index to Volume II 577

(Dates of publication, No. i, Feb. 18; No. 2, Apr. 3; No. 3, Apr.

23; No. 4, May 13; No. 5, June 16; No. 6, July 17; No. 7, Aug. 18;

No. 8, Nov. 4; No. 9, Dec; No. 10, Dec.)

ERRATA

ERRATA, VOLUME 11. e 51, Fig. 3, for constanU'^ze, read constantan. 316, fourth line from bottom, for numbers, read members.

318, line 16, transpose comma to follow days.

319, line 26, for mxture, read mixture.

319, fifth line from bottom, for supports, read supported.

Vol. II

JANUARY, 1915

No. 1

AMERICAN

JOURNAL OF BOTANY

OFFICIAL PUBLICATION OF THE BOTANICAL SOCIETY OF AMERICA

CONTENTS

Investigations on the phytogeny of the Angiospenns. 5. Foliar evi- dence as to the ancestry and early climatic environment of the Angiosperms. Edmund W. Sinnott and Irving W. Bailey i

The growth-forms of the flora of New York and vicinity.*

Norman Taylor 23

The temperature of leaves of Pinus in winter. . . .John H. Ehlers 32

PUBLISHED

IN COOPERATION WITH THE BOTANICAL SOCIETY OF AMERICA

BY THE

BROOKLYN BOTANIC GARDEN At 41 North Queen Street, Lancaster, Pa.

Entered as secoad-class matter February 21, 19 14. the post office at Lancaster, Pannsylvania, under the act of March 3, 1879.

AMERICAN JOURNAL OF BOTANY

Devoted to All Branches of Botanical Science

Established 1914

EDITED BY A COMMITTEE OF THE 6OTANICAL SOCIETY OF AMERICA

editorial committee

F. C. Newcombe, Editor-in-Chief,

University of Michigan

C. Stuart Gager, Business Manager A. S. Hitchcock,

Brooklyn Botanic Garden Bureau of Plant Industry

Irving W. Bailey, L.R.Jones,

Bussey Institution University of Wisconsin

H. H. Bartlett Edgar W. Olive,

Bureau of Plant Industry Brooklyn Botanic Garden

The Journal is published monthly, except during August and September. The subscription price is $3.06 a year to members of the Botanical Society of America; to all others $4.00. Single copies 50 cents, plus postage. Postage will be charged to all foreign countries, except Mexico, Cuba, Porto Rico, Panama Canal Zone, R,epublic of Panama, Hawaii, Philippine "islands, Guam, Samoan Islands, and Shanghai. Postage to Canada 20 cents a volume on annual subscriptions ; to all other countries in the Postal Union, 40 cents a volume on annual subscriptions.

Manuscript offered for publication should be typewritten, and proof submitted to authors should be returned as soon as possible to American Journal of Botany» Brooklyn Botanic Garden, Brooklyn, N. Y.

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Claims for missing numbers should be made within 30 days following their date of mailing. The publishers will supply missing numbers free only when they have been lost in the mails.

Correspondence concerning editorial matters should be addressed to Prof. F. C. Newcombe, 9 Geddes Heights, Ann Arbor, Mich.

Business correspondence, including notice of change of address, and directions concerning reprints, should be addressed to American Journal of Botany, Brook- lyn Botanic Garden, Brooklyn, N. Y., or 41 North Queen Street, Lancaster, Pa.

AMERICAN JOURNAL OF BOTANY

Vol. II January, 1915 No. 1

INVESTIGATIONS ON THE PHYLOGENY OF THE ANGIOSPERMS

5. Foliar Evidence as to the Ancestry and Early Climatic Environment of the Angiosperms

Edmund W. Sinnott and Irving W. Bailey

The leaf of the Angiosperms is so variable in its shape and vena- tion among closely related species and so easily modified by environ- mental influences that gross foliar characters have been largely neglected by the taxonomist and the phylogenist except within small groups of plants. A careful survey of evidence obtained from the various botanical fields, however, apparently makes possible a recon- struction of the primitive Angiosperm leaf with a reasonable degree of certainty, and a determination of some of the factors which have modified it; and thus suggests not alone the probable ancestry of the Angiosperms but also the climatic conditions under which they first appeared. The presentation of evidence on which such an hypothesis may be built is the purpose of the present paper.

It is with the more ancient of the two Angiosperm classes, the Dicotyledons, that the problem necessarily rests. The two main types of leaf venation in this group are the palmate and the pinnate, between which intermediate conditions frequently occur. Leaf shape is, of course, generally correlated with venation although there are numerous instances where broad leaves are pinnate and narrow ones palmate. The main leaf types, having reference both to venation and shape, may be roughly designated as the palmate simple (fig. 2), [The Journal for December (1 : 499-550) was issued 29 Dec. 1914.]

2

EDMUND W. SINNOTT AND IRVING W. BAILEY

palmate lobed (fig. 3), palmate compound^ (fig. 7), pinnate simple (fig. i), pinnate lobed (fig. 17) and pinnate compound (fig. 10). A brief survey of the distribution of these types throughout the three main growth forms of Dicotyledons (trees, shrubs and herbs) in various regions of the earth is set forth in the following table.^

It will be observed that in these modern floras the pinnate type is markedly predominant everywhere and that the simple pinnate condition alone constitutes from 60 per cent to 70 per cent of the species. Other noteworthy facts are the abundance of compound leaves in warm regions, the almost complete absence there of palmately lobed woody plants, and the practical confinement of the pinnately lobed type to herbaceous forms.

In view of the preponderating evidence that woody Angiosperms are more ancient than herbacous ones,^ it seems probable that leaf

^ Trifoliate leaves with stalked terminal leaflets (frequently called pinnately trifoliate) will be regarded in this paper as palmately compound.

2 Analyses have been made of the following floras as to types of leaf or types of node or both:

North America: Flora of the Northern United States and Canada, Britton and Brown; Flora of the Rocky Mountains, Coulter; Flora of the Florida Keys, Small; Flora of the British West Indian Islands, Grisebach; Flora Nicaraguensis, Goyena.

South America: Flora Brasiliensis, Martius and others; Historia de Chili: Botanica, Gay; Report of the Princeton Expedition to Patagonia: Botany, Macloskie.

Europe: English Botany, Sowerby; Flora des Ncrdostdeutschen Flachlands, Ascherson and Graebner; Flora Rossica, Ledebour; Flora des Alpes, Bouvier; Flora Espanola, Lazara; Flora Italica, Fiori and Paoletti.

Asia: Flora Orientalis, Boissier; Flora of Syria, Palestine and Sinai, Post; Flora Simlensis, Collett; Flora of the Upper Gangetic Plain, Duthie; Flora of Bom- bay, Cooke; Handbook of the Flora of Ceylon, Trimen; Maylayan Flora, King; Flora van Nederlandesch Indie, Miquel; Flora Hongkongensis, Bentham; Flora of Manila, Merrill.

Africa: Manual of the Flora of Egypt, Muschler; Flora of Tropical Africa, Oliver, Thiselton-Dyer and others; Flora Capensis, Harvey and Sonder, and others; Forests and Forest Flora of Cape Colony, Sims; Natal Plants, Wood; Plantes de Madagascar, Baillon and Castillo; Flora of Mauritius and the Seychelles, Baker.

Australasia: Flora Australiensis, Bentham; New Zealand Flora, Cheeseman.

Oceana: Flora of the Hawaiian Islands, Hillebrand; Indigenous Trees of the Hawaiian Islands, Rock.

Analyses were also made of the genera of woody Dicotyledons enumerated in Engler and Prantl's Natiirliche Pflanzenfamilien; and of the species of trees and shrubs from China and Japan in the herbarium of the Arnold Arboretum.

^ The Origin and Dispersal of Herbaceous Angiosperms. Sinnott, E. W .and Bailey, I. W., Annals of Botany, 28: Oct. 1914.

INVESTIGATIONS ON THE PHYLOGENY OF THE ANGIOSPERMS 3

Table I

p 1 s.

p 1

L. '

P 1 c. "

P' s. *

P"

L. '

P' c. '

%

%

%

%

%

%

Engler

Tropical Regions

Trees

. . . 1,326 genera

6

2

4

62

26

Shrubs

1,257 "

14

I

3

69

12

Tempevate Regions

Trees

273 "

8

6

5

60

I

19

Shrubs

776 "

7

2

5

76

2

8

iV. united omies

. . . 2,821 sps. . .

Trees

.-. 163

7

6

3

57

8

19

... 328

5

9

8

72

7

Herbs

. 2,330

II

4

10

58

6

10

Trees

73

7

5

78

4

6

Shrubs

. . . 136

I

7

15

63

14

Herbs

. . . 1,101

8

7

8

56

9

12

. . . sps.

Trees

72

13

II

5

48

6

13

306

4

9

12

55

I

19

Herbs

. . . 2,701

5

5

13

56

II

10

China

. . . 2,075 sps.

Trees

•• 501

14

10

3

56

17

Shrubs

•■• 1.574

10

6

II

62

II

542 sps.

Trees

174

12

14

2

60

II

Shrubs

... 347

7

7

13

66

7

Amazon Valley

... 2 187 sps.

Trees

941

3

.5

6

66

24

. . . 1,068

19

•5

6

65

9

Herbs

••• 178

2=^

0

8

S6

3

Madagascar

... S39 sps.

II

I

4

73

II

Hawaii

211 sps.

Trees

8

I

4

76

II

Cape Colony

. . . 3^0 sps.

9

10

68

I

12

Natal

303 sps.

Trees

50

10

6

64

20

••• 139

3

4

II

72

10

Herbs

•■• 114

6

13

6

66

8

I

4 EDMUND W. SINNOTT AND IRVING W. BAILEY

modifications among herbs are often of very recent origin and that the important steps in the foHar evolution of the Dicotyledons took place while they were practically all woody in habit.

Evidence from various sources as to the relative antiquity of the six leaf types may be outlined as follows.

Palaeobotanical Evidence

Analyses of leaf type in various Cretaceous and Tertiary dicoty- ledonous floras have been made and are presented in the following table.* Owing to the frequent impossibility of determining whether an impression is that of a palmately or pinnately compound leaf, all the compound species have been thrown together. For simplicity's sake the few pinnate lobed forms have been included with the pinnate simple ones.

It will be noted that the percentage of compound leaves in the fossil floras is smaller than in the modern ones. This is probably due in part to the fact that compound leaves are usually broken up in fossilization into their component leaflets, which have often been described as complete leaves. The most striking difference, however, between ancient and present day floras is the much greater abundance in the former of palmate leaves (32 per cent as against 13 per cent in living species). In the Cretaceous the palmate-lobed forms were as numerous as the simple ones. In the Tertiary the lobed type was

^ The following fossil floras have been examined:

Cretaceous: The Lower Cretaceous Deposits of Maryland, Berry (and others). Maryland Geological Survey; The Upper Cretaceous and Eocene Floras of South Carolina and Georgia, Berry. Professional Paper 84, U. S. G. S. ; Flora of the Da- kota Group, Lesquereux, Geol. Surv. of the Territories, Vol, VIII; Cretaceous Flora of the Territories, Lesquereux, Geol. Surv. of the Territories, Vol. VI; Flora of the Raritan Formation, Berry, Bull. 3, Geol. Surv. of New Jersey; Flora of the Amboy Clays, Newberry, Monograph XXVI, U. S. G. S.; Cretaceous Floras of Southern New York and New England, Hollick, Monograph L., U. S. G. S.; Flora Fossilis Arctica, Heer, including the Arctic, Patoot and Atane floras (Cretaceous) and those of the Polar Lands, Greenland, North Greenland, and Spitzbergen (Tertiary).

Tertiary. The Tertiary Flora of the Western Territories, Lesquereux, Geol. Surv. of the Territories, Vol. VII; The Flora of the Laramie Group, Ward, 6th Ann. Report, U. S. G. S. ; The Flora of the Bad Lands, Lesquereux, Geol. Surv. of the Territories, Vol. VIII; Flore Fossile des Travertins Anciens de Sezanne, Saporta, Mem. Soc. Geol. de France (2), VIII; Tertiarfloren der Oesterr. Monarchic, Etting- hausen, Vienna, 1851; La Flore Fossile du Japon, Nathorst, Bih. Svensk. Vetensk- Akad. Handlingar, B. 20, No. 2.

INVESTIGATIONS ON THE PHYTOGENY OF THE ANGIOSPERMS 5

Table II

Species

Palm. Simple

Palm. Lobed

Pinnate

Compound

Cretaceous

Potomac

22

6

7

6

3

S. Carol, and Georgia.

68

II

3

46

8

163

24

42

95

2

Territories

79

19

20

39

114

12

14

75

13

Amboy Clays

106

15

16

67

8

S. N. Y. and N. Eng. .

159

22

22

107

8

Arctic

32

3

I

20

8

Patoot

71

14

8

37

12

94

15

8

47

24

Total

908

14.I (is.s%)

141 (is.s%)

OOy \Oy /VJ

87 (10%)

Tertiary

205

57

12

109

27

130

40

g

68

g

34 84

12

6

10

6

24

3

48

9

178

31

II

106

30

46

13

4

24.

5

50

17

5

26

2

70

19

3

40

8

Austria

31

3

4

18

6

Japan

49

7

5

30

7

Total

877

229 (26%)

61 (7%)

479 (55%)

106 (12%)

Total of fossil floras

1,785

370 (21%)

202 (11%)

1,018 (57%)

195 (11%)

Total woody plants in

modern floras studied

7,014

661 (9%)

305 (4%)

4,578 (65%)

1,470 (21%)

little commoner than at present, but the palmate simple was much more abundant. Of course other fossil floras which are yet to be worked out, particularly those which are distinctly from tropical regions (where palmate forms are generally less numerous) may some- . times show conditions different from those which we have presented here; and fossil evidence in the present problem cannot be regarded as at all conclusive. The facts available at present, however, certainly seem to indicate that palmate leaves, particularly lobed ones, were much more abundant in earlier geologic time than at present.

Morphological Evidence I. The Important evidence toward a solution of the present

problem may be obtained from a study of the general topography of the node. One of the writers^ has shown that among Dicotyledons

5 The Anatomy of the Node as an Aid in the Classification of Angiosperms. Sinnott, E. W., Am. Jour. Botany, i: 303-322. 1914.

6

EDMUND W. SINNOTT AND IRVING W. BAILEY

the vascular supply to the leaf causes either a single gap (unilacunar type, fig. 85), three gaps (trilacunar type, figs. 83 and 84), or more than three gaps ; that these types are very constant within large groups of plants, and that the trilacunar condition is probably the most ancient of all, the other two having been derived from it by amplification or reduction. It is pointed out that the main distinction lies really be- tween the tri- and multilacunar, on the one hand (which in this paper we shall designate together as multilacunar) , and the unilacunar on the other. That the former type is almost certainly more ancient than the latter is made evident by the fact that it characterizes the vast majority of all those orders (Amentiferae, Ranales, Rosales and Malvales) which are recognized as being relatively ancient and among which are presumably to be found the most primitive living Dicotyledons. The following table, based on the genera of Dicotyledons enumerated by Engler, also shows the distribution of these two nodal types among the trees, shrubs and herbs of the Archichlamydeae and Metachla- mydeae.^

Table III

Genera. Multilacunar. Unilacunar.

A rchichlamydeae

Trees 972, 76% 909, 24%

Shrubs 794, 71% 322, 29%

Herbs 688, 59% 466, 41%

Metachlamydeae

Trees 19, 6% 269, 94%

Shrubs 199, 20% 767, 80%

Herbs 752, 43% 994, 57%

Metachlamydeae, excl. Compositae

Trees 4, 1% 269, 99%

Shrubs 26, 3% 767, 97%

Herbs 134, 10% 994, 90%

It is evident that the great majority of the Metachlamydeae (especially if we exclude the Compositae) are unilacunar and that the multilacunar forms are massed in the Archichlamydeae. The contrast is much more striking among woody plants (which are really the only ones significant in our problem) than among herbs. This predominance of the multilacunar node among the older orders and in the more primitive of the two great subclasses; and the con-

^ Analyses of nodal type are based on a study of a very large number of species in about 700 genera, from practically all the families.

INVESTIGATIONS ON THE PHYLOGENY OF THE ANGIOSPERMS 7

finement of the unilacunar type for the most part to less primitive groups, provide convincing evidence that the former condition is more ancient than the latter.

The importance of this conclusion is evident when we observe that there is a definite correlation between nodal topography and leaf type. This is indicated briefly for certain representative floras in the following table.

Table IV

Palm. S-

a m

L.

Palm

C.

Pinn. S.

Pinn

L.

Pinn

c.

2

.J

;H

'5

'S

1

%

%

%

%

%

%

%

%

/o

%

%

%

Tropical tree genera

(Engler)

64

36

ICQ

0

94

6

47

53

ICQ

0

93

7

Temperate tree genera

(Engler)

87

13

ICQ

0

93

7

52

48

100

0

97

3

Northern United States

Woody plants

92

8

ICQ

0

97

3

65

35

ICQ

0

86

14

Herbs

69

33

94

6

95

5

42

58

67

33

90

10

Great Britain

Woody plants

ICQ

0

ICQ

0

100

0

77

23

ICQ

0

91

9

54

46

88

12

99

I

36

64

79

22

95

5

Italy.

Woody plants

78

22

ICQ

0

95

5

53

47

67

33

96

4

Herbs

54

46

94

6

97

3

38

62

78

22

92

8

China.

79

21

97

3

93

7

56

44

91

9

Japan.

Woody plants

84

16

96

4

97

3

59

41

94

6

Amazon Valley

Woody plants

267

74^

ICQ

0

ICQ

0

31

69

88

12

66^

34^

83

17

93

7

30

70

67

33

ICQ

0

Hawaii.

94

6

ICQ

0

ICQ

0

35

65

100

0

South Africa.

90

10

ICQ

0

84

16

34

66

100

0

It is apparent that among woody plants the great majority of palmate simple leaves are associated with a multilacunar node,^ although this is not so evident among herbs. Practically all of the palmate lobed and palmate compound leaves, in both woody and herbaceous plants, belong to multilacunar species, and only a slightly smaller percentage of the pinnately compound leaves, as well. Fully

^ Exclusive of Melastomaceae, Woody plants, 75 25; herbs, 80-20.

^ Where the node is unilacunar with this foliar type, as among the Melastoma- ceae and certain of the Lauraceae, Verbenaceae and others, the leaf trace, although causing but a single gap, is almost always itself divided into three strands.

8

EDMUND W. SINNOTT AND IRVING W. BAILEY

half of the pinnate simple leaves, on the contrary, are connected with a unilacunar nodal type. In fact, the great majority of unilacunar plants have simple pinnate leaves. Of the 5,080 unilacunar species in the floras studied, 4,430, or 87 per cent, are characterized by foliage of this type. The pinnate-lobed type is too infrequent among woody plants to make figures derived from it of any significance. This corre- lation between venation and nodal topography is not surprising, since the single bundle of the unilacunar node would naturally tend to con- tinue as a strong midrib (fig. 85), and the isolated traces of the multi- lacunar type would readily remain isolated and produce a palmate or compound lamina (fig. 84). In fact, the three lobes of a lobed leaf and the three leaflets of a trifoliately compound one are definitely related in their ontogeny to the point of origin of the three traces.

The definite association of the unilacunar type (which seems clearly not to be primitive) with the simple pinnate leaf certainly indicates that this leaf type, now so dominant among Angiosperms, is not at all the most ancient one. The many cases where a multi- lacunar node, also, is present with this foliar form are to be regarded on such a view as the persistence of an ancient character at the node when it has been lost elsewhere in the leaf.

2. Floral Parts. The structure of certain supposedly conservative regions other than the node also furnishes evidence for the solution of our problem. One of these regions is the floral axis and its appen- dages. It is very noticeable that sepals, petals and floral bracts are often palmate in their venation when foliage leaves are otherwise. The homologies of the first two organs are still matters for debate, but bracts, at least, are almost certainly to be regarded as the morpho- logical equivalents of leaves. A few cases of palmation in floral structures are shown in figures 25 to 36. Of course there are many instances of pinnate sepals, petals and bracts but these are very rare in families where the leaves are typically palmate; and palmate floral parts are very frequent in plants with pinnate leaves. The wide- spread occurrence of palmation in floral parts may be looked upon as the persistence of an ancient character which has often been lost elsewhere.

3. The Seedling. The truth of the doctrine of recapitulation in its application to plants is frequently questioned at the present time but enough cases of conservatism in the seedling have been recorded to make evidence from this source worth seeking in any

INVESTIGATIONS ON THE PHYLOGENY OF THE ANGIOSPERMS 9

such problem as the present one. A general survey of seed-leaf characters throughout the Dicotyledons, such as may conveniently be found in Lubbock's treatise on seedlings,^ reveals the striking fact that the cotyledonary venation in the majority of cases is palmate, very often with three main veins. Not only are palmate cotyledons present in practically all palmate-leaved species but they occur (and often predominate) in every important pinnate-leaved family, as well. Some typical cases from all of the great Dicotyledonous orders are illustrated in figures 37 to 69.

The fact that the cotyledon is often broader in proportion to its length than is the vegetative leaf cannot explain its predominant palmate venation for it will be noted that in Acer, Antigonon, Rhus and many others the seed leaf is much narrower, proportionally, than the vegetative one but is nevertheless provided with three or more palmate veins. Nor can the palmate condition be explained as a physiological necessity for all seedlings, for there are numerous instances where the cotyledon is pinnate in venation. Taken in con- nection with the primitiveness of the trilacunar node, this prevalence of three-veined palmate cotyledons among Dicotyledons of all families must be regarded as important evidence that the palmate, three- veined leaf is indeed the most ancient type for the group. Should such a conclusion be clearly established, this preponderance of palmate venation in the embryo will evidently furnish an important instance of the persistence of an ancient character in plant ontogeny and will strongly support the theory of recapitulation in its application to the Angiosperms.

A somewhat similar phenomenon is provided by the peltate leaves of Tropaeolum (fig. 71), Hydrocotyle and other plants, where the early developmental stages are strongly palmate lobed (fig. 70). That this embryonic condition is ancestral for these species is indi- cated by its prevalence among closely related forms.

4. Reversions. ^There are numerous cases among plants where very vigorous growth brings about a reversion to a primitive character or intensifies its ordinary development, and it might therefore be expected that large and vigorous leaves would tend to revert to a more ancient type. In most cases there is little difference in venation among the leaves of a single plant, but numerous exceptions do occur where the largest and rankest leaves are palmate lobed whereas the

^ A Contribution to our Knowledge of Seedlings, Lubbock, J.

10

EDMUND W. SINNOTT AND IRVING W. BAILEY

smaller ones are simple palmate or pinnate. This fact is illustrated for Acer, Viburnum and Ampelopsis in figures 3, 5 and 6, 18 and 19, and 20 and 21. It has been observed by the writers in practically all families possessing palmately lobed leaves. There are also cases where a vigorous twig or stool shoot will produce this type of foliage although the typical leaf for the species is simple (figs. 72 and 73).

Evidence from morphology is therefore decidedly against the claims to primitiveness of the pinnate simple and pinnate lobed types, and as between the other four is clearly in favor of the greater antiquity of one of the palmate forms. Let us see whether such phylogenetic evidence as is available will permit a further narrowing down of the field.

Phylogenetic Evidence

Phylogenetic evidence first supports that from other sources in pointing to the simple pinnate leaf as more recent than the others, for it is overwhelmingly predominant in the Metachlamydeae. Of the 1,245 woody genera of this subclass enumerated by Engler 1,110 are simple pinnate, or 89 per cent; and of the 4,840 metachlamydeous species in the floras analyzed above, 3,780, or 78 per cent, are simple pinnate, and 400, or 8 per cent, are pinnate lobed, a total of 86 per cent. Of the 2,150 woody Metachlamydeae in these floras 1,915, or 89 per cent, have simple pinnate leaves. A type of leaf so closely associated with specialized floral structures is not likely to be very primitive. On the other hand, 70 per cent of the palmate simple type, 90 per cent of the palmate lobed, 93 per cent of the palmate compound and 88 per cent of the pinnate compound are included in the Archichlamydeae.

Of the four remaining types the pinnately compound, although developed for the most part among the Archichlamydeae, is found principally in the Juglandaceae, Rosaceae, Leguminosae, Zygophyl- aceae, Sapindaceae, Rutaceae, Simarubaceae, Burseraceae, Meliaceae, Anacardiaceae, Araliaceae, Umbelliferae, Bignoniaceae and Oleaceae, none of which are generally regarded as being particularly ancient families. On phylogenetic evidence, therefore, the pinnately com- pound leaf cannot well be considered a primitive one.

To settle our problem we should be better acquainted than at present with the phylogeny of the Angiosperms. As to just what modern families should be regarded as closest to the ancient stock

INVESTIGATIONS ON THE PHYLOGENY OF THE ANGIOSPERMS II

is as yet not definitely settled. All evidence now available, however, as to the structure of both vegetative and reproductive organs in the various families of the inclusive order Amentiferae seems to indicate clearly that this great group of simple-flowered plants is not ancient in type, as has frequently been supposed, but is rather to be looked upon as reduced and specialized. The prevalence of the simple pinnate leaf among its members is therefore no indication of the primitiveness of this foliar type. Those Dicotyledons which both from their wood structure and reproductive morphology are today winning recognition from phylogenists as being among the most ancient members of the whole class are included mainly among the simpler types of the Ranales, Rosales and Mai vales. The very great frequency of the palmate leaf, either simple, lobed or compound, among the Ranunculaceae, Saxifragaceae, Hamamelidaceae, Malvaceae and their immediate allies (over half of the palmate lobed leaves in the floras investigated belong here) thus furnishes the most important evidence that modern phylogeny can contribute to a solution of the present problem and confirms the evidence from other sources that the palmate type is indeed the' most ancient among Dicotyledons.

As to which of the three palmate forms is the oldest we cannot be quite sure. It is possible that the simple pinnate leaf with closed venation and the veins all converging at the tip of the lamina, a type which is predominant among Monocotyledons and the seed-leaves of Dicotyledons, may be the most ancient condition, from which the lobed form has arisen by a separation and divergence of the veins. The high percentage of palmate lobed leaves in the more ancient fossil floras, however; the primitiveness of the trilacunar node; the numerous cases of reversion of palmate simple to palmate lobed leaves, and the predominance of the palmate lobed form in the more primitive orders whereas the palmate simple and palmate compound types are often characteristic of more highly specialized groups, all point to the conclusion that a three-lobed, palmately three-veined leaf is one of at least very high antiquity. In such a leaf the three independent leaf trace bundles, widely separated at their insertion, probably remained so throughout their course into the lamina. In modern leaves of this type we usually find either three separate bundles in the petiole (fig. 8i) or a single three-lobed one (fig. 80) . Other leaf types generally possess a much more complicated petiolar system. If the primitive leaf was sessile or nearly so, as most writers agree, it is probable that

12 EDMUND W. SINNOTT AND IRVING W. BAILEY

the three traces went off pretty directly into the lamina as is shown in our reconstruction (fig. 83).

If the view thus set forth is a sound one we should be able to trace the transitional steps between such a primitive leaf and the various types of foliage which now occur throughout the Angiosperms.

Intermediate conditions between the palmate lobed and the pal- mate simple are to be found in several genera such as Acer, Rubus, Viburnum, Sterculia, Malus and others. In fact, the genus Acer (figs. I to 11) shows in its various species all transitions from simple pinnate to ternately compound. In many such plastic genera and families, of which the Araliaceae are another notable example, almost all leaf types may occur in closely related species and it is common to find several of them, with all sorts of intermediate conditions, even on the same plant. In all such cases vigorous growth emphasizes or restores the palmate lobed condition. In such groups as the Piperaceae, Melastomaceae and others the lobed condition seems to have been entirely lost, although the venation is still palmate. With the loss of the lobes the two lateral veins usually curve inward, some- times even giving rise to a practically closed venation.

The palmate compound type has evidently arisen from the lobed one simply by an increase in the depth of the sinuses. The various steps may often be traced in the same species or even on one indi- vidual as in species of Acer (figs. 6 and 7), Rubus, the Araliaceae and many others. Since most palmately lobed leaves have three main veins, the compound ones derived from them are for the most part trifoliate. In many cases each leaflet of a trifoliate compound leaf becomes compound, in its turn, thus giving rise to the ternately com- pound type (fig. 11).

The pinnate simple leaf seems to have had its origin from the lobed type through the disappearance of the lobes (palmate simple) and a great reduction or disappearance of the lateral veins. Number- less transitional steps may be found, especially in the more plastic genera (figs, i, 2 and 3, 12, 13 and 14). Most families which are preponderantly simple pinnate in leaf type have a few species or genera where the two basal veins are especially prominent or in which the leaf is essentially palmate. In certain cases (Rutaceae and others) the simple pinnate leaf probably represents the terminal leaflet of a reduced compound leaf.

The pinnate lobed type has apparently been derived from the

INVESTIGATIONS ON THE PHYLOGENY OF THE ANGIOSPERMS 1 3

pinnate simple by a more or less complete lateral dissection of the lamina, the lobes really representing very large leaf teeth. Transi- tions may