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BEVEL OPTVLK.TSTT OF BUDS ON BUDS AND STIPULES BY THE BIGHT HON. SIB JOHN LUBBOCK, BART., M.P. F.E.S., D.C.L., LL.D. WITH 4 COLOURED PLATES AND 340 FIGURES IN THE TEXT UNIVERSITY LONDON KEGAN PAUL, TRENCH, TEUBNEE & CO. LTD. PATERNOSTEK HOUSE, CHAEING CROSS ROAD 1899 BIOLOGY LIBRARY (The rights of translation and of reproduction are reserved) PREFACE VAUCHER long ago called attention to the fact that some species of Rock Rose have stipules while others have none, and suggested that it would be interesting, if possible, to ascertain the reason for this difference, The idea seemed to me a good one, and I devoted myself to a study of the question, with the result which will be found in the following pages. This inquiry led me on to examine the structure of buds ; and the diversity and ingenuity of the devices by which plants protect the young and tender tissues from heat, cold, drought, moisture, insects and other animals, proved so fascinating that I hoped it might not be without interest for others. The results have been printed in greater detail by the Linnean Society,1 and I have here selected those parts which seemed to me of most general interest. I have to thank Mr. THISELTON DYER, the Director of Kew Gardens, Dr. SCOTT, and the whole staff, for the facilities they have kindly afforded me. 1 ' On Stipules,' Parts i-iv. (Linnean Society's Journal — Botany, vols. xxviii, xxx, xxxiii), 1890, 1894, 1897. OF THE UNIVERSITY Of VI BUDS AND STIPULES The Trustees of the British Museum and Mr. MURRAY, the authorities of the Cambridge Botanic Gardens, and Mr. LYNCH, have also assisted me with many specimens. Dr. RENDLE has been good enough again to help me by seeing the book through the press ; and last, not least, I must cordially acknowledge how much I am indebted to my able assistant, Mr. FRASER, by whom also many of the drawings have been made. JOHN LUBBOCK. HIGH ELMS, DOWN, KENT: December 30, 1898. CONTENTS CHAPTER I ON BUDS PAGE Use of Buds— Protection of Young Tissues from Cold, Heat, Drought, Insects and other Animals — Definition of Bud- Bud of Tulip Tree — Different modes of protection — Protection by older Leaves : Begonia, Hypericum, Mesembryanthemum, Stachys, Uvaria — Protection by base of Leaf-stalk : Plane — Development of Leaves and Flowers taking sometimes a whole Year, or everr two — Frequent death of Terminal Shoot : Lime, Hornbeam, Elm, Birch, Willow, &c. — Shape of Leaves and Cotyledons — Eeasons for the differences : Mustard, Wallflower, Tulip Tree, Beech, Oak— Dormant Buds — Adventive Buds 1 CHAPTER II ON STIPULES Vaucher's Problem : Why have some Bock Roses Stipules, and others none ?— Description of Stipules — Forms and size of Stipules : Peach, Portugal Laurel, Pea, Pansy, Holly — Position of Stipules— Differences in allied Species : Elder — Differences in same Species : Hawthorn — Use of Stipules : Robinia, Petteria, Poplar, Magnolia, Astragalus, Hedysarum, Pondweed, Knotweed, Hop, Spergularia — Distribution of Stipules — Allied Species with and without Stipules : Rock Rose, Exochorda, Viburnum— The Answer to Vaucher's Problem 20 Vlii BUDS AND STIPULES CHAPTEK III ON THE DEVELOPMENT OF LEAVES AND STIPULES PAGK Origin of Leaves — The Growing-point : Aucuba, Common Laurel, Tulip Tree, Eose — Basipetal and Basifugal de- velopment : Centaurea, Galium — Ocrea : The Plane, Poly- gonum — Vernation : Conduplicate, Plicate, Circinnate, Ee- volute, Involute, Equitant, Convolute — Leaves of Water Plants — Fleshy Leaves: Mistletoe, Saxifrage, Aloe — Monocotyledons — Palms — Aroids . . . . .46 CHAPTER IV ON THE PEOTECTION OF BUDS Delicacy of Young Leaves — Grew's Description— Position as- sumed by Buds — Diminution of Eadiation— Darwin's Sug- gestion— Protection by Leaf-base, by Modified Leaves, by Leaf-stalk, by Stipules, by Connate Stipules, by Spines, by Hair, by Gum or Eesin— Protection by Older Organs : Uvaria, St. John's Wort, Berberry — Protection by Leaf -stalk : Walnut, Box Elder, Sophora, Citharexylum, Ehus, Kalmia, Plane, Philadelphus (Syringa), Actinidia, Eobinia, Broom, Whitebeam, Clematis — Protection by Stipules: Virginian Creeper, Pea, Lathyrus, Vine, Petteria, Guaiacum, Gardenia, Alstonia, Spergularia — Protection by Hairs : Polygonum amphibium, Viburnum, Horse Chestnut, Plane, Stachys, Nettle — Protection by Gum or Eesin : Horse Chestnut, Poplar, Hazel Nut, Honeysuckle, Currant, Hornbeam, Elder, Alder, Violet, Salvia, Dock, Ehubarb, Chilocarpus, Tabernaemontana 66 CHAPTEE V ON THE STEUCTUEE OF BUDS Whitebeam— Alder — Magnolia — Protection by the Leaf-base : Eose, Portugal Laurel, Maple, Ash, Horse Chestnut — Protec- tion by Leaf -blade : Lilac, Holly, Willow, Viburnum (Guelder CONTENTS IX PAGE Hose) — Protection by Leaf-stalk : Elder — Protection by Stip- ules : Leea, Pea, Hop, Virginian Creeper, Vine, Bucklandia, Passion Flower, Poplar, Lime, Birch, Beech, Hornbeam, Hazel Nut, Oak, Whitebeam — Protection by Connate Stip- ules: Elm, Wych Elm, Plane, Spanish Chestnut, Hop — Bud of Conifers — Scotch Fir— Picea — Cycas — Zamia . . 97 CHAPTEE VI ON THE FORMS OF STIPULES Great Variety of Forms — Difference of Texture— Species with -different Forms of Stipules : Hawthorn, Eibes, Quince, Poten- tilla, Nuttallia, Geum, Exochorda, Azara, Abutilon, Diplo- phractum, Catha, Ervum, Clover — Bed Clover and White Clover : Keason for Difference — Pea — Lathyrus . . . 160 CHAPTER VII ON THE SUBSIDIARY USES OF STIPULES Stipules Performing Leaf Functions : Pansy, Galium, Acacia, Lathyrus Aphaca, Adesmia — Spinous Stipules : Kobinia, Cap paris, Kibes oxyacanthoides, Bauhinia, Porlieria, Paliurus— Glandular Stipules: Viburnum, Psidium, Tropaeolum cilia- turn — As an Assistance in Climbing : Smilax, Paliurus australis — As Reserves of Nourishment : Gunnera — As Holders of Rain : Thalictrum, Viola, Polygonum — As a Sup- port: Polygonum 184 CHAPTER VIII ON THE NATURE OF STIPULES Composition of Leaf : Leaf-base with Stipules ; Leaf-stalk with Leaf-blade or Leaflets — Complete and Incomplete Leaves — Gradations in Development of Stipules : Parsley, Ostru- thium, ^Ethusa — Difficult Cases : Hypericum, Lotus, Cucumber, Helianthemum guttatum, Elder, Bryony — Views as to the nature of Stipules : (1) That they are BUDS AND STIPULES dependent on the Leaf ; (2) that they are independent organs ; (3) that they are a constituent part of the Leaf — Keasons for adopting the third view : Pansy, Galium, Plane, Polygonum— Tendrils — Monocotyledons — Stipellae —Stipules rare in Cotyledons— Composition of Leaf . . 197 CHAPTER IX SUMMAKY The Bud— Modes of Protection — Stipules : Nature of, Uses of — Fall of the Leaf : Not a case of Death, but a Vital Process ; preparation for — The Effect of Climate— Length of Life of Leaves — Pine — Spruce — Silver Fir — Yew — Pinsapo — Arau- caria — Care taken by Nature to protect Buds — Conclusion . 223 INDEX . . , 235 LIST OF ILLUSTRATIONS EXPLANATION OF THE PLATES PLATE I Frontispiece FI&. 1 Tilia vulgaris : Young Shoot. 2 The same, more advanced. 3 The same, with some of the Leaves expanded. 4 Carpinus Betulus : Young Shoot. 5 The same, to show the folding of the Leaves. PLATE II At end of book 1 Viburnum Opulus : Sprig with four opening Buds. 2 Acer platanoides : Young Shoot. 3 The same, more advanced. 4 The same, still further advanced. 5 Pyrus Aria : Sprig with three Buds. PLATE III At end of book 1 Ulmus montana : Young Shoot. 2 The same, more advanced. 3 The same, still more advanced. 4 The same, still further advanced. PLATE IV A t end of book 1-6 Leaf-buds of Fagus sylvatica in different stages of develop- ment. 7 Flower-bud of the same. Xll BUDS AND STIPULES ILLUSTRATIONS IN THE TEXT FIG. PAGE 1 Young Shoot of Tulip Tree : V ... . 2 2 Shoots of Begonia (after Potter) ,' . ' " • -..,-•" • • 3 3, 4 Young Leaves of Hypericum calycinum ... 4 5 Young Leaves of Mesembryanthemum . . . . 5 6 Young Leaves of Stachys sylvatica . . . . 5 7 Leaf of Plane, showing mode of protection of Young Bud (after Gray) • 6 8, 9 Unopened Buds of Norway Maple . . . . 7 10 Young Shoot of Lime . , . - . , . . . 8 11 Young Shoot of Hornbeam .'-.''.' . . 9 12-14 Seed, Embryo and Seedling of Eadish . . . . 11 15 Seedling of Wallflower . . .- ..>=._ .'-... 12 16 Sections of Seed of Wallflower . . '.... . . . 13 17 Arrangement of Young Leaf of Tulip Tree ... 14 18 Arrangement of Young Leaf of Tulip Tree (after Eichler) .' .... . . . . . 15 19 Winter Bud of Beech ...._,-. . . 16 20 Winter Bud of Oak .."-- . .' . . . 16 21 Achimenes Haageana, showing growth of new Plant from a Leaf-stalk (after Goebel) .... 19 22 Shoot of Helianthemum vulgare 20 23 Shoot of Helianthemum celandicum .... 21 24 Leaf of Peach \ ....'. . . . 22 25 Leaf of Portugal Laurel . . . . . .22 26 Stipules of Pea . . * ^ 23 27 Leaf of Pansy (after Colomb) 23 28 Shoot of Hymenanthera crassifolia . . . . 24 29 Young Shoot of Holly 24 30 Shoot of Guaiacum officinale 25 31 Shoot of Elder (after Bentham) 26 32 Leaves of Common Thorn 27 33 Spiny Stipules of Robinia viscosa .... 28 34 Spiny Stipules of Robinia Pseud- Acacia . . . . 28 35 Petteria ramentacea : Shoot in Winter ... 29 36 Petteria ramentacea : Shoot in Spring . . . . 29 LIST OF ILLUSTRATIONS xiii PIG. PAGE 37 Terminal Winter-bud of Black Poplar ... 29 38 Terminal Bud of MagnoUa Umbrella . . . . 30 39, 40 Astragalus chinensis, showing stipules connate at base 30 41,42 Hedysarum esculentum, showing stipules connate for their whole lengths 31 43, 44 Onobrychis sativa, showing stipules connate for the greater part of their lengths ..... 32 45 Shoot of Pondweed, showing Intrapetiolar Stipules (after Bentham) 33 46 Ocrea of Polygonum (after Gray) .... 33 47, 48 End of Shoot of Hop, showing connate Interpetiolar Stipules 34 49 Shoot of Cistus cyprius ...... 37 50 Cistus vaginatus, showing Leaf-sheath and Axillary Buds . . . 38 51-54 Leaves of Exochorda 39 55 Viburnum Lantana (after Bentham) . . . . 41 56 Viburnum Opulus (after Bentham) .... 41 57 Bud of Viburnum Opulus . . . . . . 44 58 Growing-point of Kose 46 59-63 Leaf Development in Aucubajaponica . . . . 48 64-79 Leaf Development in Common Laurel ... 49 80-82 Leaf Development in Tulip Tree 51 83-86 Axillary Buds of Tulip Tree 52 87 Growing-point of Kose . . . . . . 53 88 Section across Bud of Eose 54 89-94 Bud-scales of Rosa canina 55 95 Expanding Bud of Rosa canina . . . 56 96 Uppermost Bud-scale of Rosa canina . . . . 56 97 Basipetal Growth 58 98 Basifugal Growth 58 99 Young Leaf of Centaurea Scabiosa, showing develop- ment 59 100, 101 Leaf Development in Galium Mollugo (after Eichler) . 60 102, 103 Leaf Development in the Plane (after Eichler) . . 61 104 Diagrams illustrating Vernation (after Linnaeus) . . 63 105, 106 Shoot of Vvaria purpurea (after Potter) ... 70 107, 108 Young Leaves of Hypericum calycinum . . . 71 109 Shoot of Berberry 72 XIV BUDS AND STIPULES PIG. PAGE 110 Section across Walnut Stem and Leaf-stalk . . . 73 111, 112 Bud Protection in Negundo aceroides . 74 113 Bud Protection in Sophora japonica . . . . 75 114 Bud Protection in Citharexylum quadrangulare . 76 115 Bud Protection in Rhus glabra (after Feist) . . . 77 116, 117 Bud Protection in Kalmia latifolia .... 77 118, 119 Bud Protection in Kalmia latifolia (after Feist) . . 78 120 Bud Protection in Actinidia colomicta (after Feist) . 79 121,122 Bud Protection in Philadelphia (after Feist) . . 80 123,124 Bud Protection in Spartium junceum ... 81 125 Winter-bud of Whitebeam 82 126 Young Shoots of Virginian Creeper . . . . 83 127, 128 Tip of Vine Shoot . 84 129, 130 Shoot of Petteria 85 131, 132 Shoot of Quaiacum 86 133 End of Shoot of Gardenia florida .... 87 134 End of Shoot of Alstonia scholaris . . . . 88 135 Shoot of Spergularia rubra 88 136 Opening Shoot of Plane 91 137-139 Development of Glandular Hairs in Lilac (after Hanstein) 94 140, 141 Development of Glandular Hairs in Plane (after Hanstein) 95 142-148 Winter-buds of Alder 98,99 149-151 Bud Protection in Magnolia Yulan . ... 100 152, 153 Bud of Magnolia Umbrella 101 154-160 BudofEose . . , 103 161,162 Buds of Maple 106 163-165 Winter-buds of Ash 107 166-172 Bud-scales of Lilac 109 173-177 Winter-bud of Salix Caprea Ill 178-185 Winter-bud of Salix alba 112 186 Winter-bud of Viburnum Lantana . . . . 118 187 Stellate Hairs of Viburnum Lantana . . .118 188 Bud Protection in Leea coccinea 120 189 Shoot of Virginian Creeper 121 190 Bud Protection in Bucklandia populnea . . . 122 191-198 Winter-buds of Black Poplar 124 199-210 Winter-buds of Beech 131 211 Twig of Beech 133 LIST OF ILLUSTRATIONS XV PIG. 212 Bud of Hazel PAGE 135 213,214 Oak Buds 136 215-235 Scales of Oak Bud 137 236-246 Winter-bud of Whitebeam 141 247-260 Winter-bud of Elm 145 261 Winter-bud of Wych Elm 148 262 Outer Scales of Bud of Wych Elm 148 263-268 Winter-bud of Plane 149 269 Bud of Spanish Chestnut 151 270, 271 End of Shoot of Hop 153 272-275 Bud of Scotch Fir 154 ,155 276-285 Bud, Scales and Leaf of Picea excelsa ) *•*'*/ 157 286 162 287-291 Leaves of Bed Currant 164 ,165 292 Leaves of Nuttallia cerasiformis 169 293 Stipules of Ervum monanthos 172 294 Stipules of Ked Clover . ..... 173 295 Stipules of White Clover 174 296, 297 Stipules of Lathyrus maritimus . . . . . 175 298 Stipule of Lathyrus grandiflorus .... 176 299 Stipule of Lathyrus pratensis 176 300, 301 Stipules of Lathyrus latifolius 177 302, 303 Stipules of Lathyrus pratensis 178 304 Shoot of Lathyrus Aphaca (after Bentham) 179 305 Seedling of Lathyrus Aphaca 180 306 181 307 Shoot of Lathyrus Nissolia (after Bentham) . . 182 308 Young Shoot of Holly 184 309 Leaf of Pansy 185 310 Shoot of Acacia verticillata 186 311 Shoot of Adesmia bracteata . . . . . . 187 312 Leaf and Stipule of Tropaolum ciliatum . 193 313 Shoot of Paliurus australis 194 314 Leaf of Parsley • 199 315 Leaf of Ostruthium ...... 199 316 200 317 Leaf of Pansy . 207 318 Transverse Section of Stem of Pansy (after Colomb) . 207 319 Transverse Section of Stem of Galium Aparine (after Colomb) 208 XVI BUDS AND STIPULES FIG. PAGK 320 Ocrea of Plane . 208 321-326 Transverse Section of Stem of Plane (after Colomb) 209, 210 327-331 Transverse Section of Stem of Polygonum lapathi- folium (after Colomb) 211-213 332 Ocrea of Polygonum . , 213 333 Shoot of Potamogelon 213 334 Leaf of Desmodium canescens 217 335-338 Seed, Germination, and Seedling of Genipa clusice- folia 219,220 '339 Seedling of Species of Psychotria 221 340 Longitudinal Section through Leaf -insertion of Horse Chestnut (after Schwarz) . . . . .229 OF THE UWIVERSITY BIBLIOGRAPHY N.B. — The numibers correspond with the references in the text. 1. POTTER, M. C. Observations on the Protection of Buds in the Tropics. Journ. Linn. Soc. (Bot.), xxviii. 343 (1891). 2. VAUCHER, J. P. Sur la seve d'Aout et sur les divers Modes de D6veloppement des Arbres. Soc. Phys. et Hist, Nat. Geneve, i. 296 (1822). 3. TRISTAN, J. Memoire sur les Developpements de Bourgeons. Journ. de Physique, 1813, 401. 4. STEINHEIL, AD. Observations sur le Mode d'Accroissement des Feuilles. Ann. Sci. Nat. (ser. 2), viii. 257 (1837). 5. DE MERCKLIN, C. E. Developpement des Feuilles. Ibid. (ser. 3), vi. 215 (1846). (An abridged translation of his work, ' Zur Entwicklungs. d. Blattgestalten.' Jena, 1846.) 6. TRECUL, A. Memoire sur la Formation des Feuilles. Ibid. xx. 235 (1853). 7. SCHACHT, H. Anatomic und Physiologic, ii. (1854). 8. EICHLER, A. Zur Entwicklungsgeschichtes des Blattes (1861). 9. GOEBEL, K. Beitrage zur Morphologic u. Physiologic des Blattes. Botan. Zeit. xxxviii. 753, &c. (1880). 10. BENJAMIN, L. Ueber intrapetiolare Knospenbildung. Ibid. x. 201, &G. (1852). 11. NAUMANN, A. Beitrage zur Entwicklungsgeschichte der Palmen- blatter. Flora, Ixx. 193, &c. (1887). 12. GREW, N. Anatomy of Plants, 32 (1672). 13. FEIST, A. Ueber die Schutzeinrichtungen der Laubknospen dicotyler Laubbaume. Nova Acta Acad. Caes. Leop.-Car. li. 303 (1887). 14. GROOM, P. On Bud-protection in Dicotyledons. Trans. Linn. Soc. (ser. 2, Bot.), iii. 255 (1893). i a xviii BUDS AND STIPULES 15. HANSTEIN, J. Ueber die Organe der Harz- u. Schleim-Abson- derung in den Laubknospen. Bot. Zeit. xxvi. 697, , upper surface ; W, wing. FIG. 53.— Leaf of Exochonla Alberti, nat. size ; St, stipule. FIG. 54. — Transverse section of petiole at 3 mm. from base, x 12 ; US, upper surface. ence of stipules. The petiole of the lower leaves also sometimes shows short teeth at its upper end, which also probably represent the last trace of stipules. 40 BUDS AND STIPULES Among the Magnoliacecv, some genera have stipules, while in others they are entirely absent. In Drimys Winterij for instance, they are replaced by some of the outer leaves of the resting bud, which are reduced to bract-like fleshy scales. The leaves are convolute, the lower enclosing the upper ones. Again, in Kadsura (K. japoniccC) the winter-buds are protected by the outer leaves, which are reduced to scales, and appear to consist of flattened petioles, with a membranous margin representing stipules, free only at the tip. The true leaves follow the scales abruptly. Another very interesting case is that of Viburnum. l We have in thfs country two wild species of this genus — one, Viburnum Lantana (usually known as the Wayfaring Tree) (fig. 55) ; the other, Viburnum Opulus (fig. 56). They are not rare in woods, especially in chalky districts ; but, though very nearly allied, their leaves are remarkably different. I extract the following descriptions from Syme.2 Of V. Opulus he says : ' Leaves deciduous, stalked, roundish in outline, three-lobed, with the lobes acu- minate, coarsely toothed and ciliated, finely pubescent, but not furfuraceous beneath. Petioles with adiiate stipuliform appendages in the form of one (or some- times two) linear process on each side, a little above 1 This is taken from a paper read by me before the Linnean Society on February 20, 1890 (Journ. Linn. Soc. xxviii. p. 244). 2 In Sowerby's English Botany, 3rd ed. iv. pp. 202 and 203. ON STIPULES 41 the base.' There are, I may add, two or more honey- glands at the base of the lamina of the leaf. Of V. Lantana he says : £ Leaves very shortly stalked, without stipules, ovate-oval or elliptical-oval, dentate-serrulate, deciduous, rugose, furfuraceous- pubescent beneath, especially on the veins, at length nearly glabrous.' There are no honey-glands. FIG. 55. — VIBURNUM LANTANA. FIG. 56. — VIBURNUM OPULUS. No attempt, so far as I know, has been made to account for the difference in form of the leaf in species so nearly allied ; for the presence of the honey-glands in the one and not in the other ; nor to explain the reason for the existence of the peculiar filiform stipuli- form appendages, nothing exactly resembling which occurs in any of our other forest trees, the nearest 42 BUDS AND STIPULES approach being in the allied genus Sambucus. The presence of stipules in Viburnum would be the more remarkable, as in the family Caprifoliacece, to which the Viburnums belong, stipules (if they be stipules) are confined to this genus, to Pentapyxis, and to Sambucus. According to De Candolle's ' Prodromus,' there are forty -one species of Viburnum ; and though some more must now be added, this would not materially affect the question. Of these forty- one, thirty-five have the leaves entire, and more or less resembling those of V. Lantana. None of these possess stipules. The other six have lobed leaves, more or less like those of V. Opulus, and these all have stipuliform appendages, the existence of which would seem, therefore, to be connected with the presence of the lobes. The existence of honey-glands at the base of the leaf is also, perhaps, connected with the texture of the leaf. In F Lantana the covering of felted hairs affords a sufficient protection ; but the tender young leaves of V. Opulus would afford a tempting food to many cater- pillars and other insects. The ants and wasps which are attracted by the honey would tend to keep them down, and thus to serve as a bodyguard. Indeed, it has appeared to me that on specimens of F. Opulus, which are much frequented by wasps and ants, the leaves are less eaten than in other cases where they are not so protected. ON STIPULES 43 I now come to the stipuliform appendages. These often bear honey-glands, but by no means always, and even where these occur there seems no reason why they should be situated 011 filiform appendages. On the whole, then, I doubt whether they can be explained as mere honey-glands, or whether, indeed, they are of any actual use when the leaves are fully developed. When we meet with a small organ which appears to have no definite function, we naturally ask ourselves whether it is the disappearing relic of some larger organ which at one time performed some useful pur- pose in the economy of the animal or plant. This suggestion, however, seems untenable in the present case, because, as a matter of fact, we do not find that the stipuliform appendages are more developed in any of the species allied to V. Opulus. There is, however, a physical cause to which, per- haps, the presence of these organs may be due. We have seen that much the larger number of species of Vibur'num have entire leaves, more or less oval or ovate. This would appear to be the form typical or original to the genus. Now let us suppose that, either from having extended northwards (and both Viburnum Lantana and V. Opulus are among the northern representatives of the genus), or from some other cause, the young leaves require additional protection. This may be effected in several ways. For instance, the young leaf may be guarded 44 BUDS AND STIPULES by a thick coat of felted hairs ; this is the case in V. Lantana. Another plan would be that the outer leaves should become leathery, and thus protect the inner ones ; this is the case with F. Opulus. But that being so, it is an advantage that the inner or true leaves should be folded, because they thus occupy less space. This, perhaps, accounts for the folding of the leaves of F. Opulus in the bud, while the lobes follow from the mode in which the leaves are folded. Now a leaf folded up, as are those of F. Opulus, requires only two or three lateral veins. The remaining veins, then, and the mem- brane connecting them, will gradually be reduced, and ultimately disappear. In F. Opulus , as is shown in the figure (fig. 57), there is a space left be- Fm. 57.-BUD OF . , , . VIBURNUM Ou- tween the bases of the leaves, in the LUS, x 4. genus Acer, many species of which L, L, lateral lobes of * next; younger6 pah- have leaves somewhat resembling those oneaves; », sti- Q£ K Qpulus, this space is fully oc- cupied by the following pair of leaves. This, how- ever is not the case in V. Opulus , and the space thus left unoccupied is filled up by the stipuliform append- ages. I may also observe that the stipuliform append- ages resemble leaf-lobes in being slightly conduplicate. These considerations seem to throw some light on the differences between the leaves of Viburnum Lantana ON STIPULES 45 and V. Opulus — the hairiness of the former and the smoothness of the latter ; on the lobed form of the leaf in the latter ; and, lastly, on the presence of the honey-glands and the peculiar stip aliform appendages in F. Opulus, neither of which occur in V. Lantana. In support of the above suggestions I may refer to the interesting analogy afforded— in a totally different family — by the genus Spircea. Here we find some species with entire, some with pinnate leaves ; while those of 8. opulifolia, as the name denotes, closely resemble those of Viburnum Opulus. Now the entire- leaved species of Spircea, like those of Viburnum, have no stipules ; while Spircea opulifolia agrees with Vibur- num Opulus not only in the shape of the leaves, but in the mode of folding in the bud. and also in the presence of subulate, acuminate, stipuliform appendages. 1 might give other cases, but the above will, I think, be sufficient. It seems clear that the answer which we had provisionally arrived at from a study of the Kock/Roses is fully borne out by the examination of other families, and that when the bud needs protection and the petiole is narrowed, this function is performed by the stipules ; while, when there are no stipules, the bud is protected in some other way, and generally by the widened base of the leaf-stalk. But thougn the protection of the bud is the general, it is, as we shall presently see, by no means the only function which stipules perform in the economy of plants. 46 BUDS AND STIPULES CHAPTER III ON THE DEVELOPMENT OF LEAVES AND STIPULES IN order to arrive at a satisfactory view as to the structure and arrangement of buds it is necessary to study the development of the leaf. Steinheil (4), in 1837, was the first who approached the consideration of the subject in this rational manner; and we are also in- B S FIG. 58. — GROWING-POINT AND BEGINNING OF FIRST LEAF OF KOSE. Highly magnified. S, apex of growing-point ; li, youngest leaf ; R, cortex ; AJ, pith. debted for excellent memoirs and observations to De Mercklin (5) in 1846, Trecul (6) in 1853, Schacht (7) in 1854, Eichler (8) in 1861, Goebel (9), and others. Speaking generally, we may say that a leaf com- mences as a small conical projection immediately below the growing-point of the shoot (fig. 58). It continues to grow at its apex for a short time only, its develop- DEVELOPMENT OF LEAVES AND STIPULES 47 ment being completed by growth in a zone of cells situated just above its base (intercalary growth). So that, as Schleiden has pointed out, while the apex is the youngest part of the shoot, it is the older part of the leaf. The projection gradually widens, and often occupies more than half the circumference, thus affording a possible explanation of the fact that, while the cotyledons are opposite, the leaves are in so many cases alternate. The rudimentary leaf consists of undifferentiated cellular tissue, and does not at first contain any vessels. It is no part of my present intention to deal with this interesting subject in detail, but I will give a few cases in illustration, taking that of ordinary foliage leaves, for in those which are intended as bud-pro- tectors the stages are very different. AUCUBA On account of its simplicity, I will commence with the common Aucuba japonica of our shrubberies. The leaves of Aucuba are opposite, ovate, and without stip- ules. They commence as two slight projections, each of which broadens at the base, and finally occupies one- half of the circumference of the stem (figs. 59, 60), so that they are concave on the inner side and almost cover over the growing-point. They gradually elongate (fig. 61), and from being at first slightly curved 48 BUDS AND STIPULES round the stem, become folded lengthways or con- duplicate. They are clothed with long, sparse hairs, and show a few teeth, or rather knobs, along the edge, one terminating each of the veins, which are thicker than in subsequent stages (fig. 63). The teeth, or m FIGS. 59-62. FIG. 63. AUCUBA JAPONICA. Highly magnified. FIG. 59, first pair of leaves, front view ; FIG. 60, ditto, side view ; Fio. 61, ?econd pair ; FIG. 62, ditto, more developed ; FIG. 63, third pair. knobs, are also much larger in proportion than in the full-grown leaf. COMMON LAUREL The subjoined figures illustrate the structure of the bud of a Common Laurel (Cerasus Laurocerasus). DEVELOPMENT OF LEAVES AND STIPULES 49 Here again the leaf commences as a small projection or lobe immediately below the growing-point. Very soon . .A. •k MB? MHP * ^ /\ COMMON LAUREL. FJGS. 64-70, leaves and their stipules ; s, s, stipules ; x 10. FIGS. 71-79, outer scales. two other lobes appear at the base of the first (fig. 64, s,s). These are the stipules. They are at first much smaller E 50 BUDS AND STIPULES than the leaf. By the time, however, that the leaf-blade has reached -g-^th inch (fig. 67) the stipules have caught it up. They are more oval, more pointed, and bordered by a row of small projections. They continue to grow (fig. 68) more rapidly than the leaf-blade, and some- what unequally (fig. 69), the larger one becoming rather more (fig. 70), the shorter one rather less, than double as long as the leaf-blade. Then comes a some- what abrupt transition, and the outer scales do not, of course, correspond to stages in the development of a normal leaf. A rudimentary leaf, such as that in fig. 70, is followed by a scale of quite a different form : broader, wrapping round the bud, and consisting of three parts nearly but not quite equal in length, and separated almost to the base (fig. 71) ; the two outer pieces representing the stipules are rather broader than the central. In the next (fig. 72) the leaf-blade is rather longer than the stipules, and the common stalk or leaf-base is longer in proportion. This is still more the case in the next two (figs. 73, 74). In the twelfth (fig. 75) the leaf-stalk is abruptly trun- cated ; and in the following the stalk and stipules are reduced to three small prominences. Finally, the outer scale is much shorter and broader in proportion (fig. 79). THE TULIP TREE (Liriodendron tulipifera) In the Tulip Tree the leaf commences as a slight projection immediately below the growing-point, and DEVELOPMENT OF LEAVES ANT) STIPULES 51 gradually widens into a ridge, the two ends of which eventually meet, forming a ring. One part raises itself above the rest and forms the leaf-stalk ; the two side pieces become the stipules. They grow upwards and inwards, finally forming a hood over the growing-point. About the time when 81 82 TULIP TUBE (Liriodendron tnlipifcra). FlG. 80.— Very young leaf and stipule, x 20. FIG. 81.- Do. do. second stage, x 20. 'FIG. 82.— Do. do. rather more advanced stage, x 20. the stipules meet the leaf-blade commences. It is at first a very narrow, delicate, hyaline membrane. The bud then assumes the appearance shown in fig. 80. The next stage (fig. 81) shows the growth of the leaf-blade, which is more developed in fig. 82. Fig. 17, p. 14, shows how closely the young leaf fits in the E'2 52 BUDS AND STIPULES hollow of the bud ; while the final arrangement of the leaf in the bud is shown in figs. 17 and 18. In the axillary buds, as a rule, the outer covering consists of two stipules, the rest of the leaf not being developed (fig. 83). Sometimes, however, at the base a small projection may be seen (fig. 84), which is a 83 84 85 86 FIGS. 83-86. — TULIP THEE. Outlines of different axillary buds. rudiment of a petiole. Sometimes this is rather more developed (fig. 85), and sometimes a rudimentary blade also appears (fig. 86). The reversal of the leaf in the bud, owing to the length and early development of the petiole, is very unusual. In Amicia Zycjomeris the leaf is bent, but only forms a right angle with the petiole. ROSE The leaf of the Rose (see ante, fig. 58, p. 46) is more complicated. It commences as a small knob at the side of, and immediately below, the growing-point. When this knob has reached a certain length it pre- sents two lobes (fig. 87), which arise almost simul- taneously.1 The upper of these becomes one of the 1 According to Schacht, however, the stipule appears first. DEVELOPMENT OF LEAVES AND STIPULES 53 upper leaflets, the lower is one of the stipules. Almost immediately a third, and then a fourth, lobe make their appearance. The third is the rudiment of a leaflet of the second pair, the fourth of the third. Thus the stipule appears almost simultaneously with the first and upper leaflet, before any of the lower FIG. 87.— GROWING-POINT OF EOSE WITH Two LEAVES IN SUCCESSIVE STAGES OP DEVELOPMENT. Highly magnified. and later ones. These originate close above the stipules. Gradually, however, the petiole elongates, thus carrying the lower leaflets away from the stipule. De Candolle described the stipules as being connate 54 BUDS AND STIPULES with the petiole. This, however, is not, I think, strictly correct. The true petiole is the leaf-stalk above the stipules. The winged part below is really a develop- ment of the leaf-base. Adnate stipules, as these are called, arising from a similar development of the leaf-base, occur in many FIG. 88. — SECTION ACROSS THE Bur> or A ROSE. A, growing-point ; Ll, youngest leaf ; L2, three folded lobes of second leaf ; St2, stipules of second leaf ; Sc'-Sc% scales. other cases, as, for instance, in some Lupins, Clovers, Potentilla, &c. That winged petioles are not always stipular is, however, shown by the case of Lathyrus • for instance, L. silvestris. DEVELOPMENT OF LEAVES AND STIPULES 55 The rudimentary leaves in the Rose pass gradually into the bud-scales ; the transition is not so abrupt as in the Aucuba or in Maples (fig. 8, p. 7). If we examine a Rose-bud in winter, the first or outermost scale (fig. 89) is unequally triangular, as a rule acute, carinate, and small. The second one is very similar, at least in the case of lateral buds. The third scale (fig. 90) is much larger, and rounded at the apex, or occasionally emarginate by the breaking away of the tip, and more or less strongly carinate. The 89 90 91 92 93 94 BUD-SCALES OP EOSA CANINA, x 2. FIG. 89, first scale ; FIG. 90, third do. ; FIG. 91, fourth do. ; FIG. 92, fifth do. ; FIG. 93, sixth do. ; FIG. 94, ninth do. fourth scale (fig. 91) is twice as large as the third, broad at the apex and tridentate, the middle tooth representing the petiole, and the more obtuse lateral ones the stipules. The fifth scale (fig. 92) is rather narrower, but covers about half of the bud, and the middle tooth is slightly the longest. Thexsixth scale (fig. 93) is the longest, surmounting the bud, and folded round it so as to cover about three-fourths of its surface ; the three teeth are about equal in length. From this point onwards the scales get rapidly shorter and smaller. With this difference the seventh and eighth scales are 56 BUDS AND STIPULES similar to the sixth; they are rolled round the bud, covering about seven-eighths of its surface, and over- lapping at their apex. The middle tooth at the apex has slightly increased in length. This is even more evident in the ninth (fig. 94) and tenth scales, both of which are small. FIG. 96. , FIG. 95. EOSA CANINA. FIG. 95. — Stem bearing expanding lateral bud, x 2 ; one scale has fallen, revealing its axillary bud (b) ; five scales are shown, and two of the first leaves. Sketched March 24. FIG. 96.— Uppermost scale, immediately preceding the first true leaf, x 2 ; L, unde- veloped blade ; st, st, stipules. The eleventh scale may be described as the first normal leaf, though still rather imperfect. The leaflets are represented by small or narrow teeth, crowded together. The stipules are now well developed, and much larger in proportion to the rest of the organ than DEVELOPMENT OF LEAVES AND STIPULES 57 in previous cases. The second leaf, occurring at the twelfth node, has a more elongated lamina, though still rather imperfect. The stipules are well developed, and as in the previous case, they cover about three -fourths of the bud. Succeeding ones are very minute, and appear to be perfect leaves. No free petiole is to be seen at this stage of the bud in winter, the stipules being adnate along the whole length of the midrify so that the lamina of the leaf is sessile. The above description was made from an average bud on a strong shoot. Buds on weak shoots have fewer scales. Buds examined in January were still dor- mant, or nearly so ; and this applies to most or all of the British Eoses. Some exotic species, such as Rosa indica, R. multiflora, and others of that type, are almost burst- ing into leaf at the same date, if the weather is at all mild. The appearance of a developing bud in spring, with one leaf nearly expanded, is given in fig. 95. In the Rose, as we have seen, the development of the leaflets proceeds from above downwards, the upper leaflets being the older. This mode of growth, there- fore, has 'been termed ' basipetal' (fig. 97). The same sequence is followed by many other Roscicece, Valeriana, Melianthus, Reseda, Grasses, Cyperaceoe, Lilies, Orchids, and probably all Monocotyledons. On the other hand, there are also species in which the reverse takes place — i.e., in which the lowest lobes are the oldest, and others are developed upwards, i.e., 58 BUDS AND STIPULES are basifugal (fig. 98), as in the Pea, Ailanthus, Maho- nia, &c. A similar difference in the mode of growth may be shown to occur even when there are no leaflets. Thus, Steinheil made a nick with a knife on a young growing leaf of Mesembryanihemwn, half way up, and found that in the full-grown leaf it was much nearer the apex than the base. M. deltoideum has a number of small fleshy points, especially one at the summit, and two at each side. These are in proportion much nearer /h FIG. 97. — To ILLUSTRATE FIG. 98. — To ILLUSTRATE BASIPETAL GROWTH. BASIFUGAL GROWTH. the base in the young than in the full-grown leaf. Again, in Urtica biloba the notch at the apex of the leaf, from which the species takes its name, reaches in the young leaf to the centre, but in the full-grown leaf only a third or a quarter of the length. In pinnate leaves the insertions of the pinnae are, as Steinheil says, marks written by Nature on the leaves, and when, as in many cases, they are nearer together at the base, the upper leaflets are the older and the lower ones younger. Thus, a growing leaf of Asclepias syriaca may have six DEVELOPMENT OF LEAVES AND STIPULES 59 pairs of lateral nerves in the upper half of the leaf and eighteen in the lower. In the perfect leaf, on the contrary, each half bears thirteen. In some cases, however, the growth of the leaf as a whole and that of the separate leaflets follows different lines. Trecul, moreover, has shown that the development of leaves cannot in all cases be brought under these two categories. In Oentaurea, for instance (fig. 99), the central lobe is formed first, and others appear successively, both up- wards and downwards. There has been much difference of opinion whether any, and, if so, what, other modes of development exist in addition to those already mentioned, but from my special LEAP OP CENTAUREA . . f, . . . SCABIOSA, x 14. The point of View it IS not necessary to larger leaf embraces go into this question. FIG. 99. — YOUNG a younger one at its GALIUM The following figures, after Eichler, illustrate the development of the leaf in the Ladies' Bedstraw (Galium Mottuyo). Fig. 100 gives a vertical view of the tip of a shoot. Round the central growing-point is a nearly circular ridge. Immediately below this is another ridge, which shows a number of small emi- nences— two larger, right and left, which are the rudi- 60 BUDS AND STIPULES merits of the leaf-blades ; and four smaller, at the four corners, which represent the rudiments of the four leaf-like stipules, two belonging to each leaf. Fig. 101 represents a rather more advanced stage, in which two other knobs (one of which is already indicated at the top of the left-hand figure) have made their appearance, which complete the ring of , Fm. 100. FIG. 101. LEAF DEVELOPMENT IN GALIUM MOLLUGO. Highly magnified. eight so-called leaves. This figure is taken from a lower node, the leaves of which will be at right angles to those of the previous node. Hence the leaf-rudi- ments which were to the right and left in the first figure now stand above and below, while the last added rudiments stand right and left. The four true stipule- rudiments still occupy the corners. Some leaves have what is known as an * ocrea.' This is a sheath which, taking its origin at the base of the leaf, surrounds the stem above it for a greater or less distance. Ocreas occur in the Plane, Dock (Rumex), Polygonum, Pondweed (Potamogeton), &c. DEVELOPMENT OF LEAVES AND STIPULES 61 THE PLANE (PLATANUS) The leaf of the Plane originates in a ridge which ,-0' FIGS. 102, 103. — LEAF DEVELOPMENT IN PLATANUS OCCIDENTALIS. The upper figure shows the growth of the first leaf-ridge (o1) round the growing- point, A. The ridge is not yet complete, being still open towards the front. The outermost row of cells is the inner surface of the base of the protecting leaf-stalk. The lower figure (transverse section) shows three leaf-ridges (oSo'.o3) surrounding the growing- point, A. The youngest ridge (o1) is still incomplete. runs round the whole axis immediately below the grow- ing-point. 62 BUDS AND STIPULES At one place it raises itself more than elsewhere, and develops two side processes — the two primary leaf- lobes. These soon develop two side lobes. In the meanwhile the conjoined stipules gradually close over the growing-point, and finally cover it entirely. They do not, however, coalesce in the centre, but only touch. At a later period the edges turn outwards and assume a leaf-like form (fig. 136). The account given by Benjamin (10) is somewhat different, but I believe that of Eichler, confirmed by Mikosch, is substantially correct. POLYGONUM In Polygonum also the leaf arises as a small projec- tion just below the growing-point, and gradually ex- tends round it. This ring, which originates the primordial leaf, is higher at one place, which will develop into the leaf-blade. The rest of the ring grows and extends across the base of the leaf until it entirely surrounds the growing-point, forming the ocrea, and often projects some way beyond the growing-point. It completely covers the bud, which, however, eventually forces its way through. VERNATION The attitude of leaves in their very young stage is termed by botanists ' vernation.' Some lie flat, as, for DEVELOPMENT OF LEAVES AND STIPULES 63 instance, the Mistletoe and Mesembryanthemum. This is usually the case with fleshy leaves. Among the most common modes of folding are the following, which are illustrated by the diagrams in fig. 104. 1. Conduplicate : when folded lengthways, doubled up on the midrib, as in the Rose, Bramble, Tulip Tree (fig. 104, A). B O JJ £ . /' FIG. 104. — DIAGRAMS ILLUSTRATING VERNATION. 2. Plicate, or plaited : when folded like a fan on the ribs, as in the Maples, Currant, and most palmate leaves (fig. B). 3. Circinate : when coiled like a crozier, as in the Ferns, Drosera, &c. (fig. C). 4. Revolute : when rolled backwards from the mar- gins, as in Azalea, Rosemary, and many plants of hot, dry places (fig. D). 5. Involute: when rolled inwards from the margins, as in Violets, Water Lilies, &c. (fig. E). 64 BUDS AND STIPULES 6. Equitant : when the leaves are folded one over the other, as in Grasses, Sedges, Iris, and many other Monocotyledons (fig. F). 7. Convolute : when rolled up from one margin — i.e. one margin within, the other without the coil, as in the Cherry, Peach, Pea, Vetch, &c. (fig. G). There are sometimes considerable differences be- tween nearly allied species ; and in some cases the outer and inner leaves of the bud assume different positions. The conduplicate arrangement seems to follow natu- rally from the mode of development described on p. 47. The rudiment of the leaf, spreading more or less round the growing-point, assumes a hollow form, and when it rises above the central axis would thus become folded on itself. In pinnate leaves generally, as in those of the Rose, each leaflet is conduplicate. In palmate leaves the folded arrangement is that naturally best calculated to enable them to fit into the bud. The involute and revolute types perhaps have refer- ence to the later life of the leaf, as affording a certain protection against too rapid transpiration. The equitant type follows naturally from the mode of growth of many Monocotyledons. Leaves of the same form may be folded in very different ways, and it is seldom that the same plan runs through a whole family, at least among Dicotyledons. DEVELOPMENT OF LEAVES AND STIPULES 65 The leaves of water-plants are as a rule flat or rolled, not folded. The consistence of the leaf exercises much in- fluence, for thick, leathery, or fleshy leaves, such as those of Mistletoe (Viscum), Aloe, many Crassulas, Saxifragas, &c., naturally are as a rule flat ; some- times rolled ; but rarely folded. Pinnate and trifoliate leaves are generally folded. In Monocotyledons the leaf rises as an elevation immediately below the growing-point, gradually sur- rounding part of the stem, and highest at the point opposite the opening. The ridge extends until it forms a sheath more or less completely surrounding the stem. The leaves of Palms and Aroids develop in a manner very unlike that usual among Dicotyledons. The leal originally forms a continuous blade, which is much folded, and subsequently divides. According to Eichler, this is effected by a process of disorganisa- tion at the edge of the fold. A similar process occurs in the segmentation of the originally entire thallus of species of Laminaria, a common genus of brown sea- weed. Naumann (11), on the contrary, maintains that the cells along the line of the fold detach themselves and diverge from one another. I believe, however, that Eichler's view is correct. 66 BUDS AND STIPULES CHAPTER IV ON THE PROTECTION OF BUDS YOUNG leaves are extremely delicate. They require protection from too great heat, cold, dryness, moisture, and light, as well as against the attacks of animals. For this purpose they are often provided with a covering of more or less woolly hair, which generally drops off when it has served its purpose. In other cases the outer envelopes of the bud are specially modified for the purpose. As Grew (12) quaintly says : ' According to the Form and Foulding of every Leaf or Gormen, is its Protection order'd ; about six ways whereof may be observed ; sc. by Leaves, Surfoyls, Interfoyls, Stalks, Hoods, and Mantlings. To add to what we have above given, one or two Instances. Every Bud, besides its proper Leaves, is covered with divers Leafy Pamiicles, or Surfoyls ; which, what the Leaves are to one another, are that to them all. For not opening except gradually, they admit not the Weather, Wet, Sun or Air, to approach the Leaves, except by degrees respondent, and as they are gradually inur'd to bear them. Some- times, besides Surfoyls, there are also many Interfoyls ON THE PROTECTION OF BUDS 67 set betwixt the Leaves, from the Circumference to the Center of the Bud; as in the Hasel.' Here he uses the term ' Surfoyls ' for the outer scales, whatever their true character may be. His ' Interfoyls ' are stipules. Besides the protection afforded by actual coverings, the opening buds in many cases guard themselves, to some extent, at any rate, by assuming either an erect position, as in the Whitebeam (Pyrus Aria) (PL II. fig. 5), Acer platanoides (PL II. figs. 2-4), and, I be- lieve, most shrubs with opposite leaves ; or a drooping attitude, as in the Lime (Tilia) (PL I. figs. 1-3), Beech (Fagus) (PL IV.), Hazel Nut (Corylus), Elm (Ulmus) (PL III.), &c. The great leaves of Palms are at first vertical. One advantage thus gained is that the radiation is much less than it would be if the leaves were to assume at once their permanent horizontal position. Darwin has shown that this position really does tend to check the effect of radiation. Our experiments, he says, ' show that leaves compelled to remain horizontal at night suffered much more injury from frost than those which were allowed to assume their normal vertical position.' } 1 We exposed on two occasions during the summer to a clear sky several pinned-open leaflets of Trifolium , which naturally rise at night, and of Oxrdis 1 Movements of Plants, p. 286. F2 68 BUDS AND STIPULES •purpurea, which naturally sink at night (the plants growing out of doors), and looked at them early on several successive mornings, after they had assumed their diurnal positions. The difference in the amount of dew on the pinned-open leaflets and on those which had gone to sleep was generally conspicuous, the latter being sometimes absolutely dry. whilst the leaflets which had been horizontal were coated with large beads of dew. This shows how much cooler the leaflets fully exposed to the zenith must have become than those which stood almost vertically, either upwards or downwards, during the night. ' From the several cases above given there can be no doubt that the position of the leaves at night affects their temperature through radiation to such a degree that, when exposed to a clear sky during a frost, it is a question of life and death.' 1 It is probable, however, that in some cases, at any rate, this position is assumed as a protection against too intense light. The principal modes by which buds are protected are : 1. By the expanded base of the preceding leaf. 2. By scales which represent modified outer leaves. as in Willows, Ash. 3. By the outer leaf-stalks, as in Maples, Ash. 4. By stipules, as in the Beech, Oak. 1 Loc. cit. p. 293. ON THE PROTECTION OF BUDS 69 5. By the two connate stipules of a leaf, as in the Elm, Spanish Chestnut. 6. By two connate stipules belonging to different leaves, as in the Hop. 7. By spines. 8. By furry hair. 9. By gum, resin, or mucus. In considering the protection of buds in their youngest stages we must distinguish between two different cases : the first, where the young bud as a whole is protected by older organs; and the second, when the future leaves are protected by the outer bud- scales. The cases in which the young bud is protected by older organs may be divided into four principal cate- gories : 1. Those in which the protection is mainly afforded by leaf-blades. 2. Those in which the protection is mainly afforded by the petiole or by the leaf-base. 3. Those in which the protection is mainly afforded by stipules. 4. Those in which the protection is mainly afforded by hairs. PROTECTION BY LEAVES In hot countries, where the young bud principally requires protection from the scorching rays of the sun, this is often effected by their simply lying under the 70 BUDS AND STIPULES shelter of older leaves. A good example is afforded by Uvaria purpurea, which has been described and figured by Mr. Potter (1 , 349) . ' A front and also a back view of a shoot of this plant are shown in figs. 105 FIG. 105. FIG. 106. SHOOT OF UVAHIA PURPUREA. FIG. 105, front view. FIG. 106, back view. and 106, where fig. 105 is the front view and fig. 106 the back view of a similar shoot. The shoots themselves are in this plant slightly inclined to the vertical, so that by this means the younger leaves are protected from the sun's ON THE PROTECTION OF BUDS 71 heat. On examining the front view (fig. 105), we see that the three leaves a, &, c, are so arranged that they com- pletely cover over the growing-point and its younger leaves, so that these latter are completely shielded ; while the back view (fig. 106) shows how the younger FIG. 107. FIG. 108. SHOOT OF ST. JOHN'S WOKT (Hypericum), showing protection of the young pair of leaves (B). FIG. 107.— Side view. FIG. 108.— Front view. internodes, with their smaller leaves, are hidden behind the large leaves. The young leaves as they attain to their mature size assume the same relative positions, and so protect other young leaves, and so on.' I have already referred (ante, pp. 4, 5) to the cases of Begonia and Ehubarb. 72 BUDS AND STIPULES In other cases the leaves form successively a more or less complete covering for those that follow, as, for instance, in the St. John's Wort (Hypericum) (figs. 107, 108). In the Common Barberry (Berb&ris vulgaris) (fig. 109) the primary leaves are changed into spines. The bud, however, in the axils of these spinose leaves develops into a short axis with. ,, |j foliage leaves. This is why the leaves in this species are collected in tufts. In Azima tetracantha (a member of the Salvador acece, a small tropical family of Di- cotyledons) the axillary buds are rather remarkable. What FIG. 109.-Sn OF BAR- aPPear to be tw° SPin6S BERRY (Berberis vulgaris), ated in the axil of the leaf showing three spines, Sp, representing the leaf. Nat. are really the first pair of A, stem'; L,L) leaves on a lateral leaV6S °f the Axillary shoot. SSfc^i^aS6^^^ In their early stages they are red uced to short, subulate spines ; , , , . -. , L', L', more perfect leaves on the erect, closely applied, and very same lateral shoot. J short, but when fully developed they become hard, spiny, and diverging. Their foliar nature is further indicated by the fact that a slender groove runs along the opposing faces from apex to base, where there is a deeper cavity, as if a sheath were attempted. They are also articulated with the ON THE PROTECTION OF BUDS 73 stem. The second and third pairs of leaves on the axillary shoot (when the latter develops) are reduced to scales, which decussate with the spines. True leaves follow the scales. PROTECTION BY THE LEAF-EASE OR THE LEAF-STALK The axillary buds are thus protected in most Composites, Umbellifers, in the whole family of the Caryophyllacece (Pink family), except Spergula and Spergularia, in the Gentians, and many other families. In all these species the base of the petiole is more or less dilated, so as the more effec- tually to protect the bud. *• FIG. 110. — SECTION ACROSS Fig. 110 represents a sec- THE STEM OF A WALNUT. , • , I f L, petiole : 11. bud ; 8, shoot. tion across the stem of a Walnut (Juglans nigra). It shows the bud, B, lying between the stem, 8, and the dilated base of the leaf-stalk, L. The protection is more complete than the figure indicates, because in nature the parts touch, while for clearness a small space has been left between them in the illustration. In the Box Elder (Negundo acerddes) (figs. 111,112), a near ally of the Maples, the base of the petiole is also widened, concave, almost covering the axillary bud, and attached to the axis by a wide and deeply horse- shoe-shaped base. The interior of the concavity is 74 BUDS AND STIPULES densely lined with white silky hairs, which almost completely surround the axillary bud, keeping it safe and comfortable till the fall of the leaf. The terminal bud nestles in the cavity between the petioles of the youngest expanded or expanding pair of leaves. The petioles of the latter remain erect for a consider- able time, and being closely applied face to face, FIG. ill. FIG. 112. NEGUNDO ACEKOIDES. Nat. size. FIG. 111.— Portion of shoot (A) with the bases of the two opposite leaf-stalks (p). PIG. 112. — Vertical section of same, showing the axillary buds (B) sheltered in the hollowed base of the leaf -stalk. they completely cover and protect the bud. When growth becomes arrested for the season the terminal bud attains some size, so that its tip projects beyond the cavity of the petioles. By this time, however, the scales of the winter-bud are sufficiently hardened to escape harm and protect the younger members. In Sophora japonica (fig. 113), one of the Legumi- nosce, the terminal bud is thickly covered with brown ON THPJ PROTECTION OF BUDS 75 hairs, and is also protected by the crowding of the leaves and the stipules. The latter are narrowly linear or seta- ceous and caducous, i.e., falling early. The axillary bud is entirely protected by the swollen, fleshy base of the petiole. The resting bud remains very small during winter, and consists of leaves and stipules, crowded together, and densely covered with short, brown hairs. In Citharexylum quadran- gulare (fig. 114), belonging to the Verbenacece, an exstipulate family, the axillary buds are completely covered by the concave pedestal. The terminal bud in the FlG- HS.-SOPHOBA JAPONICA. Nat. size. growing State Consists of leaves Two nodes of a stem, the lower showing the base of the petiole "Dartlv COnduplicate, then in- (P') with the small round scar of J the fallen stipule. In vertical volute at the margins, and ?*£*&• J^FSSfc placed face to face, but not SSfiflf *STh» "5 & , . . , , , . petiole (P"). overlapping or interlocking with one another. The leaves attain some size before expanding, and each pair covers the next younger pair. In some cases the petiole forms a regular arch over the bud, as, for instance, in Elius glabra (fig. 115). Addi- tional protection is also afforded by hairs, both on the bud and on the under side of the cup formed by the petiole. 76 BUDS AND STIPULES In these cases the overarching tissue belongs entirely to the petiole. In others the stern also projects out- wards, and thus makes the protection more complete. FlG. 114. — ClTHAREXYLUM QUADRANGULARE. Nat. size. a.r, fl.r, axis of shoot with portions of a pair of leaves ; a a, articulation of the leaves, I, I, to the persistent sheathing pedestals, one of which, p, is slightly opened to show the axillary bud it covers. In Kalmia latifolia, for instance (figs. 116-119), the axis of every shoot produces an outgrowth opposite the dilated portion of the petiole. ON THE PROTECTION OF BUDS 77 This is carried still further in Actinidia colomida . 120), where, as Feist (13) has shown, "the bark of FlG. 115.— KlIUS GLABRA. Section through a bud shortly before the leaf falls. S, stem /,, base of leaf-stalk. Enlarged. FIG. 110. FIG. 117. SHOOT OF KALMIA JATIFOLIA, x 2. Fio. 116.— s, swelling of the stem just above the base of the loaf (L), between which and the leaf-base the bud is sheltered. FIG. 117.— Another view. £c, scar of leaf ; s, swelling ; B .bud. 78 BUDS AND STIPULES the stem throws out a process which almost meets that of the petiole. A still further advance in the efficient protection of the bud by the petiole occurs in those species — as, for instance, in the Plane (Platanus^ fig. 7, p. 6) — where the lower part of the petiole has closed completely round the bud, covering it like an extinguisher : in such species the bud is not where we should naturally expect to find it, namely, in the angle between the petiole and FIG. lift. FIG. 119. KALMIA LATIFOLIA. Small piece of shoot, entire (fig. 118), and enlarged in vertical section (fig. 119). S, stem ; A, swelling in stem ; L, leaf -stalk. the stem, but enclosed in the base of the petiole itself. For such buds the term c intrapetiolar ' was proposed by Benjamin, who first called special attention to them. In these cases, however, the protection seems to fail just when it might seem to be most needed. At the approach of winter the leaf falls off, leaving the bud uncovered. Being thus thrown on its own resources, it is compelled to protect itself, and we shall presently ON THE PROTECTION OF BUDS 79 consider the various plans which have been adopted with this object. By that time, indeed, the tissues have become hardened, and more capable of resistance to external influences. It would seem, however, that it would have been an advantage if the petiole of the Plane, instead of detaching itself at the base, had separated higher up, thus leaving a cap to protect the young bud. This, in fact, does happen in other cases. Thus, in Philadelphus (the Sweet Syringa of our gardens and shrubberies), in Actinidia oolomicta (fig. 120) (accord- ing to Hildebrand), RoUnia, and some other species, if we examine a shoot, we shall at first see no traces of buds. Fig. 121 gives a section through such a twig of Pldladelplms at one of the joints, on the right side before, and on the left after, the fall of the leaf. Fig. 122 gives a section of one side of a similar knob, more magnified ; a a shows the line along which the leaf L will detach itself, leaving a pedestal, which completely protects the bud, by the growth of which it FIG. 120. — ACTINIDIA COLOMICTA. Section shortly before the leaf falls ; bud completely covered. S, stem ; /,, leaf ; a a, plane of separation of leaf. 80 BUDS AND STIPULES is eventually pushed off. Intrapetiolar buds also occur in Sldmmia japonica, Xanthoxylon Bimgei, &c. It will be observed that the leaf-stalk does not detach itself, as in the Plane, at the base, but a little higher up, thus leaving a sort of cap, which for clearness is repre- sented in the figure as a little detached, but which in nature fits closely over the bud, and remains till spring, when it is pushed off by the expanding leaves. The L FIG. 121. FIG. 122. PHILADELPHIA CORONAKIUS. FIG. 121. — Small piece of shoot. FIG. 122 — Portion of fig. 121 much enlarged a a, line along which the leaf detaches itself. cavity is also lined by a thick felt of brown, hollow, air-containing hairs, which no doubt serve as a very effective non-conductor of heat. If the brown cap is removed the green bud will be found snugly ensconced under it. The bud in the Robinia, like that of Pliiladelplms, is completely covered by the base of the petiole. If we examine the scar left by the leaf, we shall find, as pointed out by Benjamin, a broad, irregular, ON THE PROTECTION BUDS 81 somewhat pointed hump, from each side of which the two stipules project as spines. The bud is not visible, but occupies a hollow in this eminence, which is, in fact, formed by the persistent base of the petiole. The cavity, as in Philadelphus, is lined by a thick felt of brown, hollow, air-containing hairs. The protection of the bud in Berleris resembles that in FIG. 124. SHOOT OF SrAKTitiM JUNCEUM. FIG. 123. — Reduced one-half. FIG. 124. — Part of same shoot, to show the bud protectrd by the pedestal of the fallen leaf ; nat. size. .#, bud ; P, persistent pedestal of leaf. In Spartium j'imceum (figs. 123, 124) there are no stipules, but the bud is protected by the enlarged, concave, persistent pedestals of the last year's leaves. A similar arrangement occurs in the Broom (Cy- tisus scoparius) and other species of Cytisus, while the terminal bud is protected by two small scales and a dense covering of hair. G 82 BUDS AND STIPULES In Genista tinctoria the stipules are subulate-tri- angular, acute, short, and seated on the persistent and elongated pedestal of the leaf. The winter-bud is also protected by scales, consisting of reduced leaves, on which the stipules are scarcely perceptible. In Genista antardica and G. sagittalis the stipules are similar but even more minute. In G. virgata the shoots die at the tips, so that there are no ter- minal buds. The pedestals are densely lined with Lairs on the inner surface. In the Whitebeam (Pyrus Aria) (fig. 125) also the outer scales are the base of the last year's leaf-stalks. A similar arrangement occurs in Clematis crispa. Protection by pedestals oc- curs in various other members of the families Rosacece, Pom- acew, Amygdalacecv, &c. It is by no means confined to species with intrapetiolar buds. In these cases the bud is protected by the leaf-stalk, or the leaf-base of the leaf in the axil of which it is situated. PROTECTION BY STIPULES We now come to cases in which buds are protected by the stipules of the mother-leaf. This may be said FIG. 125. — WHITEBEAM (Pyrus Aria). WINTER-BUD. p p, persistent base of fallen peti- oles ; ab, axillary bud ; ss, se- cond scale. ON THE PROTECTION OF BUDS 83 to be the function which stipules most frequently per- form. See, for instance, Plates L, III., IV. As a general rule such stipules fall with the leaf to FIG. 126.-- YOUNG SHOUT OF VIRGINIAN GBEKPEK, x 2. */, stipule ; (, tendril. which they belong. In some cases, however, as in Pette- ria (figs. 129, 130), they persist, and thus form a more effective, or at least more permanent, protection to the young bud. o2 84 BUDS AND STIPULES There are, moreover, some cases in which stipules are developed so early that they serve not only to protect the younger leaves, but even the blade of the leaf to which they belong, as, for instance, in the Common Pea (fig. 26, p. 23), Lathyrus maritimus (fig. 296, p. 175), &c., Virgi- nian Creeper (fig. 126), Vine (figs. 127,128),Hop (fig. 48, p. 34). These will be alluded to in a subsequent chapter. FIG. 127. FIG. 128. VINE (Vitis vinifera). FIG. 127.— Tip of growing shoot, nat. size; l\l',l\ three youug leaves in order of succession ; Stl, 8t'2,St3, one of the pair of stipules belonging to each of the three leaves ; f, tendril with its bract removed, showing the first fork. FIG. 128. — Apical bud after removing the three leaves shown in fig.127, x 5; Z4, the fourth leaf in succession ; St*, one of the stipules belonging to I* ; Sts, a stipule belonging to the fifth leaf ; t, tendril almost enclosed in its bract ; 6, the bract, a modified leaf with three nerves in the sheathing base, which appears to consist of stipules adnate to the base of the petiole. In Petteria mmentacea (figs. 129, 130) the stipules are at first small and obtuse. They have a covering of hair, and are axillary and slightly connate. The leaves are deciduous, but their stipules are persistent, and swell up or grow to considerable size, becoming thick and fleshy. Every lateral bud is, therefore, completely covered and effectually protected by the pair of stipules belonging to the leaf of the preceding year. These ON THE PROTECTION OF BUDS 85 St. -Sc stipules, as well as the persistent pedestal of the leaf to which they are attached, are densely lined on the inner face with pale brown hairs like a thick fur, while they are glabrous and dull olive-green externally. In Guaiacum qffidnale (figs. 131, 132) the stipules are axillary and connate into a rounded piece on each side of the stem on which they are inserted, covering the space between the petioles, but quite free from them. They persist even after the leaves have fallen, and be- come only gradually broken away from the top down- wards. In Gardenia florida (fig. 133) also the four stipules of the two opposite leaves are connate, and form a sheath, which encloses the younger parts of the bud. In Alstonia scholaris, belonging to the Apocynacece, the leaves (fig. 134) are whorled at the apex of each shoot in groups of six to nine, narrowly oblong- elliptic, narrowed to both ends, but obtusely pointed. The short petioles are semi-terete, flattened above, and furnished with a ligule or outgrowth from the base of the upper face, protecting the bud. This ligule is FIG. 129. FIG. 130. PETTEKIA RAMENTACEA. FIG. 129. — Portion of shoot in winter, x 2. FIG. 130.— Ditto in spring, x 2. Sc, scar of fallen leaf ; St, stipules completely covering the bud in fig. 129, in fig. 130 pushed aside by the developing bud (fe). 86 BUDS AND STIPULES triangular, obtuse, pale green, l'5-2 mm. long; collec- tively they form a whorl, covering all but the extreme apex of the bud. (See also 14.) In Spergularia rubra (fig. 135) the leaves are opposite, long, narrow, fleshy, and somewhat flattened above. The -St. FIG. 132 FIG. 131 GUAIACUM OFFICINALE. FIG. 131. — Terminal shoot, nat. size ; n, node ; st', connate stipules ; st", connate stipules covering the terminal bud. FIG. 132. — Terminal shoot with lamina of leaves removed, x 2 ; st' st", stipules as in fig. 131 ; b, lateral bud. stipules1 are scarious, inserted at the node just be- neath the leaves, so that they pass round the back of the latter, completely enclosing them in bud, and covering their bases even when fully developed. This is a most unusual arrangement. The stipules are also 1 See Dickson, Journ. Bot. 1878, p. 316. ON THE PROTECTION OF BUDS 87 connate at the base, with an interpetiolar, free, ovate, acute piece, which is sometimes entire, sometimes divided at the apex into two or three setaceous teeth, as if these free portions consisted of one stipule from each LFm. 133. — END OF SHOOT OF GAUDEXIA FLOKIDA. Nat. size. //, L', a pair of leaves with their connate stipules, St', showing the fissured side only ; L", L", the youngest unexpanded pair of leaves, with their stipules (St"} completely investing the terminal bud. leaf united. These stipules are very advanced in bud, and evidently attain full size long before the expansion of the leaves, many pairs of which they completely cover and protect. They are persistent, covering the bases of the leaves when full grown. They thus pro- 88 BUDS AND STIPULES tect the terminal and axillary buds, the latter being very freely produced. The stipules in this case may be compared to the FIG. 134. — ALSTONIA SCHOLAEIS. Terminal FIG. 185. — SPERGULARIA whorl of leaves to show ligules cover- RUBRA, x 3. ing the bud. Keduced about one-half. s, stipule ; L, leaf. ocreas or sheathing and scarious stipules of the Poly- gonacece. The stipules of the latter are, however, ON THE PROTECTION OF BUDS 89 continuous with the edges ot the petiole, which appears as a strong midrib to the sheath ; while those of Spergularia are perfectly free from the leaves. PROTECTION BY HAIRS In other cases buds are protected by hairs. These fall into three main categories : 1. Hairs which form a felt or fur. 2. Stiff, bristly hairs. 3. Glands. Many species are glabrous, or hairy, according to the conditions in which they live ; for instance, there is a com- mon English Polygonum which, from growing sometimes on land and sometimes in water, is known as P. amplii- Hum. Land specimens are hairy, especially at the nodes, while specimens growing in water have no hairs. It has been suggested that the hairs at the nodes prevent small climbing insects, such as ants, from reach- ing the flower, which they would rob of its honey without rendering any service in return in the way of cross-pol- lination. When growing in water the plant obviously needs no such protection. Protection by Fur or Felt Hairs forming a fur or felt may act in various ways ; as, for instance : 1. By warding off excessive moisture. 2. By preventing too much transpiration. 3. By protecting the buds from excessive cold. 90 BUDS AND STIPULES 4. By making the buds unpalatable or inaccessible to insects. 5. By toning down the light. In some cases, as in Mullein (Verbasciim), the whole plant is covered with felted hairs. In the Wayfaring Tree (Viburnum Lantana) (fig. 186, p. 1 18) the outer leaves of the bud protect the inner, but they all develop, and suffer very little from the cold, as they are protected by a thick coat of stellate hairs, which cross and intercross, thus forming a sort of grey felt. In the Dogwood (Cornus sanguinea), Buck- thorn (Ehamnus Frangula), and others, the young leaves are similarly protected. In the Vine, again, the bud is covered only by a felt of hairs. Lastly, in some plants, as in the Horse Chestnut (^Esculus Hippocastanum) and Plane (Pfatarws), some of the scales protecting the bud are hairy. In the Plane (Plcdcmiis) the stipules are connate, the upper part being turned over in a sort of frill, so that they almost resemble a green flower, from the centre of which the stalk emerges (fig. 136). If the base of the leaf-stalk be examined, it will be found, as we have already seen, to form a regular cap, protecting the bud. After the leaves have fallen the winter-buds are covered by several cap-like stipules (see figs. 263—268), the leaves belonging to which have become completely aborted. The outer stipule or cap is brown or reddish brown, and secretes a gummy substance on its inner sur- ON THE PROTECTION OF BUDS 91 face, besmearing the bud as in the Horse Chestnut, but only in the very early stages. As the bud swells the outer cap becomes ruptured, and appears then like a deeply concave scale, which is gla- brous, or nearly so. This is followed by others, which attain a somewhat larger size before the expanding bud causes them to split ; they are densely covered with brown hairs exter- nally and glabrous inter- nally. In the Horse Chestnut the fur is on the young leaves themselves. In this species, as in many others, the hairs drop off when the leaf expands and their func- tion is fulfilled. Virgilia lutea and Gym- nocladus, both members of Leguminosce, and Pterocarya, an ally of the Walnut, may be mentioned as other cases in which the bud is well protected by furry hairs. Protection by Stiff Hairs In many cases, as, for instance, in the common Stachys (8. sylvatica) (fig. 6, p. 5) and its allies, the bud is protected by stiff hairs. FIG. 136. — OPENING SHOOT OF PLANE. Two-thirds nat. size. L , I/', successive leaves with their stipules, St\ ,ST-. 92 BUDS AND STIPULES In certain species such hairs contain an acrid liquid, as in the Common Nettle (Urtica dioica). Protection by stiff hairs occurs also among the La- biatce in Galeopsis (6r. Tetrahit and versicolor) ; among the Boraginece in Ecliium, Lycopsis, Borago, Anchusa ; among the Loasece in Loasa ; among the Leguminosce in Mucuna ; Saxifragece in Davidsonia ; MalpigJiiaceoB in Malpighia, &c. These hairs constitute, however, a protection to the plant as a whole, rather than to the buds specially. Protection ly Gum, Resin, or Turpentine In other cases buds are protected by gummy or resinous secretions, as in the Horse Chestnut (^Esculus), the Poplar (Populus), Hazel Nut (Gorylus\ Honeysuckle (Lonwercb)^ Currant (Ribes), Lilac (Syringa), Hornbeam (Carpinus), Elder (Sambucus), and Alder (Alnus\ in many herbaceous plants (Viola, Helianthus, Salvia), and most Conifers. The gum is often confined to the outer surface, the interspaces between the leaves being filled by hairs. The gum or resin is secreted by hairs, by glands, by leaf-teeth, or by the general epidermis. The gum cells are generally developed early, and are short-lived. The secretion lessens transpiration, and in many cases also serves to protect the young leaves from insects and other animals. Smaller insects would get legs ON THE PROTECTION OF BUDS 93 and wings clogged by the sticky secretion, and the scent or taste would act as a deterrent to browsing animals. Glandular Hairs Glandular hairs sometimes take the form of papillae, and are in many species club-shaped, or resemble large- headed pins ; they are often richly coloured, as, for instance, in some of the Currants, Geraniums, &c., glittering in sunlight like emeralds or rubies. They often develop very early, showing that they are in- tended to protect the young and tender leaves. In such cases they soon wither away ; in others, however, they persist as long as the leaf, especially in hot arid dry countries, which are particularly rich in aromatic plants. Pleasant as is their smell — that, for instance, of the Lavender — such plants are too astringent to be eaten, and are thus protected from browsing quadrupeds. The secretion may be either a gum, which, for instance, is richly secreted in the buds of some species of Polygonum ; or a resin ; or both may be present together. The resin, according to Hanstein (15), is generally secreted in the interior of the cells, and oozes through the cell wall, while the mucus is generally the product of the epidermis. The properties and functions of the two are no doubt different. Some plants secrete both, as, for instance, the Horse Chestnut. 94 BUDS A^D STIPULES The development of such glandular hairs in Lilac is shown in figs. 137-139. A cell raises itself somewhat above the general level of the leaf, and becomes cut off by a transverse wall (fig. 137, a, fr; fig. 138, a). It then divides into two transversely, the upper cell form- ing the head of the pin (fig. 138, fr), which may divide again by vertical and transverse walls (fig. 139). As a general rule special hairs develop themselves into glands. In the Plane (figs. 140, 141), however, we find a remarkable combination of the two. The hairs FIG. 139. DEVELOPMENT OF STALKEI> GLANDULAR SECHETING HAIKS IN LILAC (Syringa vulgaris). In fig. 139, ft, the stalk has not been formed. branch, and one fork may remain a simple pointed hair, while another develops a gland. The glandular processes are sometimes highly deve- loped; as, for instance, in the Eose and the Violet, where they are large and oval, one being formed at the tip of each tooth of the leaf. In the Docks (Rumex), Polygonum, and Rhubarb (Rheum) the buds secrete a copious mucus, which in some of the larger species can even be squeezed out ON THE PROTECTION OF BUDS 95 in a drop. It is formed by papillary outgrowths of the epidermis. The buds of Chilocarpus look as if they were covered by red sealing-wax (16). «* FIGS. 140, 141. — DEVELOPMENT OF HAIRS IN PLANE (Platanus acerifolia). An epidermal cell divides into two unequal parts by an oblique wall. The upper grows out into a 2 -4-celled hair, the apical cell of which becomes a spherical gland-cell ; a lateral cell grows out obliquely into a long, pointed, hair-like structure. The lower figure shows the development, the upper the perfect form of the hairs. The case of Taberncemontana (l,35i) is especially interesting. The buds of this plant are covered with a 96 BUDS AND STIPULES gum which does not completely harden, but remains in a semi-fluid condition ; and as the leaves previously covered up grow and expand, the gum remains attached to their edges, and stretches as a thin film between them. Thus the next youngest leaves are for a certain time enclosed in a small four-sided chamber, two oppo- side sides of which are formed by two leaves, and the other two opposite sides by a thin film of gum. The gum is eventually ruptured and the same process is repeated. Glands are present in the axils of the leaves in the great majority of Crucifers (Norman says in nine-tenths), in most Lyihrariew, and in many others. The connection of these glands with the protection of the young and highly delicate leaf is further shown by their very early development. In fact, in some spe- cies there is a stage in which the glands are actually larger than the rudiment of the leaf itself. They are, however, often very transitory. 97 CHAPTER Y ON THE STRUCTURE OF BUDS HAVING thus glanced at the various ways in which buds are protected by other and older structures, let us now see how they behave when they are, so to say, thrown on their own resources. In doing so I will, as far as possible, take in illustration our familiar forest trees and other common plants. It is in some respects difficult to draw a hard-and- fast line between the buds now to be considered and those described in the last chapter. In the Whitebeam (Pyrus Aria) (fig. 125, p. 82), for instance, the pedestal of the last leaf of the previous year is persistent, and, no doubt, of some use to the very young bud ; but I class it here because in the main the shelter is due to the outer, modified stipules belonging to the bud itself. It is remarkable how many devices Nature has adopted, and how much even nearly allied groups, such, for instance, as the Willows and Poplars, differ from one another. It is, indeed, a very general, though not invariable, rule that the outer envelopes of winter-buds are formed 98 BUDS AND STIPULES of brown, more or less leathery scales ; but as we shall see, these scales represent very different organs. If we examine the bud of an Alder (Alnus glutinosa) (figs. 142, 143, 144) in winter, we shall find that it is FIG. 143. BUD OF ALDEE (Alnus glutinosa). FIG. 142.— Portion of shoot, showing two lateral buds in winter ; Sc, scar of fallen stipule, leaving L, the corresponding leaf, exposed ; St, the stipule of the next leaf ; the upper bud shows only one stipule, St, but none have fallen in this instance, which is the more common case. Nat. size. FIG. 143.— Transverse section of bud in winter, x6 ; A, A, first or outermost pair of stipules, belonging to the leaf immediately beneath them ; B, B, second pair of stipules with their leaf ; c, c, third pair ; the fourth leaf, D, D, and stipules occupy the centre ; Ax, axis. protected by three, or sometimes four, purplish brown, leathery scales. The lateral buds sit on gradually elon- OS THE STRUCTURE OF BUDS 99 gating pedestals. If there are three scales, these are stipules. When four are present, one will be found to have at the end a few finger-like processes (fig. 142, L), the rudiment of a leaf-blade. At the base will be found the more or less evident scars left by the two stipules. C. S. '140 o.st 144 147 ALNUS GLUTINOSA, x 3. FIG. 144. — Portion of slioot bearing a lateral bud ; o.s., outer scale ; s.s., second scale — that, is, the outer one of a pair of stipules. Fio. 145.— Outer scale of winter-bud. FIG. 146.— o.s., outer, and i.s., inner stipule of the first distinct pair ; Z, their leaf, flattened out like the stipules. FIG. 147.— o.s?., outer, and i.st., inner stipule of the second distinct pair ; I, their leaf. FIG. 148.— o.st., outer, and i.st., inner stipule of the third distinct pair ; I, their leaf. In this case, therefore, the last leaf of autumn is small, and sooner or later falls off ; but, in connection with the stipules of the next leaf, it often assists in protecting the bud through the winter. It often, however, be- comes detached, and in such buds as shown in the trans- H 2 100 BUDS AND STIPULES verse section (fig. 143) the young leaf-blades are pro- tected by three stipules, two belonging to the outer leaf, the third to that next following. Here, therefore, though the main protection is afforded by stipules, the leaf-stalk and leaf-blade of an older leaf sometimes take a part in it. • „ I u- 1 FIG. 149. FIG. 150. FIG. 151. MAGNOLIA YULAN, x 2. FIG. 149.— Shows uppermost leaf with its stipules protecting the terminal bud in autumn ; b, bud in the axil of the next lower leaf which has fallen. FIG. 150 . — Second stage, shows aborted leaf, a, the stipules of which protect the winter-bud. FIG. 151. — Side view of same. The second pair of stipules (fig. 147) of the more typical lateral buds are free, unequal, imbricate, and completely cover their own leaf and two out of the three sides of the more or less trigonous bud. The outer stipule ON THE STRUCTURE OF BUDS 101 of this second pair is ovate, more or less exposed along the middle and at the apex, which is curved, the exposed portions being more coriaceous than the rest. The inner of the two is half-ovate; pale green, and membranous. Both are traversed longitudinally by slender parallel FIG. 152. FIG. 153. TEEMINAL BUD OF MAGNOLIA UMBEELLA, x 1^. FIG. 152. — Uppermost leaf still present. FIG. 153. — Uppermost leaf has fallen, leaving only a pedestal, p ; its stipules remain to protect the winter-bud. nerves. The leaf in connection with the second pair is lanceolate-oblong, acute, serrate, glandular, and plicate along the course of the ascending nerves. It is more or less folded over the younger members of the bud. All the leaves and stipules are glued together by a viscid, resinous, fragrant gum, secreted by glands. The third pair of stipules (fig. 148) are slightlvun- 102 BUDS AND STIPULES equal, narrowly ovate or lanceolate, membranous, and more faintly nerved than the previous pair. The outer stipule envelops about two-thirds of the bud, including its fellow-stipule and the leaf. The latter is ovate- elliptic and folded over the younger members of the bud as a rule. The fourth pair of stipules and their leaf (fig. 148) are sometimes very similar to the preced- ing set, sometimes much smaller. This difference is apparently due to the relative vigour of the axis bearing them. A somewhat similar case is afforded by certain species of Magnolia. In Magnolia Yulan the stipules of the uppermost leaf protect the young bud in autumn (fig. 149), but when it drops the stipules fall with it. This leaves a small undeveloped leaf-blade (fig. 150, a), which soon perishes. The stipules belonging to it, however, remain, and form a silky case, which protects the bud. The* leaf-blade corresponding to a, therefore, is useless and wasted. Another species (Magnolia Umbrella) (figs. 152, 153) avoids this waste of power and material. When the last leaf of the year dies and drops off, the stipules belonging to it remain and protect the bud (fig. 153). Under these circumstances the leaf corresponding to a, which in Magnolia Yulan perishes uselessly, in Magnolia Umbrella is still retained, and develops into the first leaf of the following year. In M. Soulangiana, a garden hybrid, there is a similar arrangement. ON THE STRUCTURE OF BUDS 103 PROTECTION BY THE LEAF-BASE ROSE The bud of the Rose in December (figs. 1 54-9) consists of a number of scales with three more or less well-marked 154 155 156 158 159 SCALES OF EOSE-BUD. FIG. 154. first scale : Fir:. 155, third do. ; FIG. 150, fourth do. ; FIG. 157, fifth do. ; FIG. 158, sixth do. ; FKJ. 159, ninth do. projections at the apex. In this case the scale itself represents the leaf-base, while the stipules and upper FIG. 160.— EXPANDING BUD OF EOSE. Stem bearing expanding lateral bud, x 2 ; one scale has fallen, revealing: its axillary bud (b) ; five scales are shown, and two of the first leave-;. Sketched March 21. part of the leaf are indicated by the three points. The outermost scale is the shortest, and they gradually 104 BUDS AND STIPULES increase in length. After about ten of such scales the little leaf-blade becomes much larger, and the leaf- base smaller, in proportion (see fig. 160). PORTUGAL LAUREL (Prunus lusilanico) The bud-scales of the Portugal Laurel are also leaf- bases. They are serially continuous with the leaves. The first scale covers less than half the bud and overlaps the second slightly at the base. It presents three points at the apex, or rather two points with a blunt process between them. These are the rudiments of the petiole and stipules. The second scale is longer, but otherwise not materially different. The third scale attains the full length of the bud, the petiole being more acuminate than in the previous scale, and longer than its stipules. The fourth scale is precisely similar, and covers more than half of the bud. All the stipules are ciliate and serrulate. The fifth scale is shorter, and much more rounded at the base. It covers three-quarters of the bud or more. The sixth and seventh scales are smaller and shorter than the previous ones, and cover the bud, with the exception of a small slit at the base, where the edges of the stipules do not come in contact. At the eighth node in the terminal bud examined the first true leaf occurred. It was small, subulate, slightly conduplicate, but colourless, and much shorter and narrower than its green and ciliate-serrulate stipules. ON THE STRUCTUEE OF BUDS 105 The ninth and tenth nodes bear leaves somewhat better developed, but their stipules are smaller and narrower. The fourth leaf, at the eleventh node of the bud,, is conduplicate, and as long and about as wide as its stipules, without being unfolded. Succeeding leaves and stipules are very much smaller in the bud at this stage, but otherwise similar to the fourth. It will be noted that the stipules become almost separate from their leaf from the first one onwards, even in the bud stage. The stipules are deciduous, falling before the end of the summer. MAPLE (Acer) In species which have no stipules there is nothing to distinguish the base of the leaf from the petiole. Thus, if we look at the winter-bud of a Sycamore, a Maple (figs. 161, 162), or a Horse Chestnut, we find it covered by a number of brown, leathery scales, which are, like the leaves, opposite and decussate, so that one might at first sight be disposed to regard them as a simple form of leaf. On looking more closely, however, we shall soon find one which shows a scar or three small teeth at the summit. When the plant begins to grow in spring some of the scales, especially on certain trees, enlarge somewhat, and show small but often well- developed leaf-blades at their tip. In the Norway Maple (PI. II. figs. 2-4) these scales enlarge and assume a OF THE UNIVERSITY OF 106 BUDS AND STIPULES beautiful red colour, so that the growing bud looks almost like an opening flower. These bud- scales, therefore, are evidently the bases of leaf-stalks. If, without waiting for the spring, we open a bud •i FIG. 161. FIG. 162. BUDS OF MAPLE. F.IG. 161.— Leaf-bud. FIG. 162.— Flower-bud. in summer, say in July, we shall find five or six pairs of scales, each pair at right angles with the pre- ceding, and then a beautiful little crown of tender green leaves. Fig. 161 shows such a bud, drawn in December, after the removal of one of the last pair of scales. The remaining scale is shown forming a large hood over the little leaves, which at Christmas only occupy about half the space in the bud. ON THE STRUCTURE OF BUDS 107 Other buds (fig. 162) contain flowers. Both are lovely, and I do not know which is the more exquisite. ASH (Fraxinus) The buds of the Ash (Fraximis excelsior) (figs. 163-5) are olive-green, so dark as to be almost black. Tennyson, in the ' Gardener's Daughter/ describes Juliet's hair as More black than ash-buds in the front of March. The stems are much paler. The lateral buds are almost completely covered by the two outer scales. The FIG. 163. FIG. 164. Asn BUDS. Nat. size. FIG. 165. In fig. 164 and fig. 165 successive pairs of scales have been removed from the terminal bud. scales of the terminal bud are often more or less bent. The scales are leaf-stalks, and generally show more or less rudimentary leaflets at the tip. The outer scales are 108 BUDS AND STIPULES thick, and rather furry on the inner side. The second pair are furry on the outer side, and especially on the edges. The third pair still more so. The outer scales are not dead, like those of so many trees, but increase more or less in size. The dark colour is due to a layer of black, more or less angular bodies, which are flattened hairs, containing a dark resinous secretion, and do not increase in size or number. As the scale grows they are, therefore, carried further and further apart, and occupying a smaller relative portion of the surface, the general colour becomes lighter and greener. HORSE CHESTNUT The bud of the Horse Chestnut (JEsculus Hippocas- tamvm) is protected by eight or' ten scales. The outer ones are dark brown and short ; they are serially continuous with the leaves of the preceding year. Those following become gradually longer and paler — often pinkish towards the end. The inner ones have a delicate fringe along their, edges. The outside of the bud is very sticky. The scales are followed by normal leaves. Each segment of the leaf is conduplicate, and the midribs of the first, as well as the petiole and the internodes, are further protected by a thick felt, which is sometimes of a rich orange colour. This is less developed on the inner leaves, where it would not be so much wanted. ON THE STRUCTUKE OF BUDS 109 PROTECTION BY LEAF-BLADE LILAC (Syringa) The bud of a Lilac (Syringa vulgaris) at first sight closely resembles that of a Maple or Horse FIGS. 166-172. — LILAC, SHOWING SEPARATED BUD-SCALES. Enlarged. Chestnut, but the real structure is quite different. Each scale here represents a leaf-blade. The first pair (fig. 166) are short and broad; the second (fig. 167) are somewhat longer and pointed; the third 110 BUDS AND STIPULES (fig. 168) are longer than broad; the fourth (fig. 169) still longer, and rather narrowed at the base ; the fifth (fig. 170) begin to assume the form of the leaf, and have a distinct, though very short, base; the sixth and seventh (figs. 171, 172) approximate still more to the final form of the leaf. In the Holly also (Ilex Aquifolium) the bud-scales are leaf-blades. THE WILLOW (Salix) The winter-buds of the Goat Willow (Salix Gaprea) are ovate, obtuse, tumid, relatively short, and more or less downy. The terminal bud dies, so that growth is renewed by the lateral ones. The bud is covered by a cap or scale in one piece, which shows no line of cohesion on either the anterior (fig. 173) or posterior face (fig. 174). Laterally, however, there are two strong ribs or keels, one on each edge. When growth recommences in spring the scale splits regularly from apex to base on the posterior face, and from the apex downwards, for one-third to one-half its length, on the anterior face (fig. 175). If the scale splits further, it does so irregularly. The whole scale, flattened out at fig. 176, shows the extent of the natural splitting, and also the two ribs or keels. This method of splitting and the two ribs indicate that the scale of the winter-bud is composed of two leaves, inserted right and left on the axis and cohering ON THE STRUCTURE OF BUDS 111 by their anterior and posterior edges. The first leaf- blade (fig. 177) is roundly ovate, obtuse, densely silky on the back and edges, and thinly hairy on the inner face. The second and third leaf-blades are oval-oblong, obtuse, and narrower. The fourth is oblong and more narrowed to the base. The fifth is lanceolate ; and the sixth and seventh are very similar. The eighth leaf- 177 173 SALIX CAPREA. FIG. 173. — Portion of shoot with a lateral bud; s, scar of fallen leaf; s.st., scar of fallen stipule. FIG. 174. — Posterior view of the same bud. FIG. 175.— Anterior view of another bud bursting, showing the silky leaves, I, I ; w.s.t winter-scale. FIG. 176. — Another view of the same scale removed and spread out, showing two midribs, m, m ; a.e., anterior edges, slit naturally ; p.r., posterior edges, slit to the base naturally on the bursting of the bud. FIG. 177.— The first leaf from the bud. blade is more decidedly narrowed to the base, and when in situ is more completely rolled round the bud than the previous ones, almost entirely covering it. It will be seen that there is little difference between the lengths ot the first eight leaf-blades. The ninth, tenth, and eleventh leaves are very similar to the 112 BUDS AND STIPULES eighth, but much shorter and smaller. The stipules are large, particularly on the leafy shoots ; but they develop after the leaves are expanded, or during that process. Some forms are exstipulate. The winter-buds of the White Willow (Salix alba) are all axillary ; the terminal one, as well as the tip of every shoot, dies. The buds are oblong, obtuse or sub- acute, compressed antero-posteriorly, but tumid on the 178 179 180 182 183 184 185 SALIX ALBA. FIG. 178. — Anterior aspect of winter-bud covered with one scale. FIG. 179.— Posterior aspect of the same, showing the median thickened suture, s. FIG. 180.— Scales of winter-buds bursting along the suture on the posterior aspect, showing the mass of leaves, I, bent at the apex. FIG. 181.— First true leaf, immediately inside the winter-scale. FIG. 182.— Second leaf. FIG. 183.— Fifth leaf. FIG. 184.— Eighth leaf. FIG. 185.— Tenth leaf. anterior face (fig. 178), thickened at the edges, and have a thickened suture (fig. 179) along the middle of the posterior aspect. The cap-like scale seems to consist of two leaves united ; its thickened edges and the strong, slightly branched nerve, easily seen on the inner face of these thickened edges, tend to support this view ; but no suture is discernible on the ante- rior face. When growth recommences in spring, the scale bursts along the suture on the posterior face (fig. 180). ON THE STRUCTURE OF BUDS 113 When the tip of the scale dies in winter, it breaks off during the bursting of the bud; and when the whole of it dies, the growing leaves rupture it at its insertion on the stem. The first normal leaf-blade (fig. 181) is ovate, flat- tened on the posterior face against the axis, incurved at the sides, covering two-thirds of the bud. Both the dorsal and inner faces are silky ; the edges are ciliate. The second leaf-blade (fig. 182) is very similar. The third is smaller, and covers about three-quarters of the bud, but otherwise is similar. The fourth is smaller, but covers about seven-eighths of the bud. The fifth (fig. 183) is lanceolate and very much smaller, but otherwise similar to previous ones. The sixth leaf covers the 'bud, with the exception of a small slit at the base ; but the seventh overlaps at its edges, completely enclosing the bud. The eighth leaf (fig. 1 84) is very small and membranous. The ninth leaf is membranous and almost glabrous ; while the tenth (fig. 185) is lanceolate, acuminate, subtransparent, glabrous, and minute. All these smaller leaves are completely convolute, and they gradually open at the edges as the younger members of the bud become bulky. The stipules are minute or undeveloped in the winter-buds. The convolute vernation of the leaves, and their silky, densely ciliate character amply protect the younger members. The bursting of the winter- I 114 BUDS AND STIPULES scale along the posterior face allows it to prolong its period of protection. I have been in some doubt with respect to the nature of the scale covering the winter-buds, but have come to the conclusion that this scale consists of two modified leaves, connate by their margins along the median line of the posterior and anterior aspect of the bud respectively. The following reasons seem to justify this view : 1. The scale in all the eleven species examined burst along the posterior face, generally to the base. Salixpyrifolia and S. reticulata are exceptions, inasmuch as they generally split at first a little more than halfway down. The swelling of the axis completes this operation later on. 2. There is sometimes a ridge on the posterior face corresponding to the line of union, as in 8. alba and 8. cinerea. In S. cordata there is a wide shallow groove at the same place. o. The anterior face during the expansion of the buds in spring becomes emarginate, bidentate, or more or less deeply bifid at the upper end. S. alba and S. luoida are exceptions, inasmuch as the anterior face remains entire. I have observed no ridge, indicating union, on the anterior face ; but as this is generally absent or inconspicuous on the posterior face, it does not much invalidate the presumed cohesion of the anterior edges of the leaves. ON THE STRUCTURE OF BUDS 115 4. Another strong reason for regarding the outer sheath as representing a pair of leaves is that it is more or less carinate on the edges, right and left —that is, laterally. The inner face shows a number of longitudinal, parallel nerves, the two strongest of which occupy the position of the carina or keel, and correspond to the midribs of the two leaves. The mid- ribs being right and left of the bud, agree with the insertion of the first two leaves of axillary buds, those leaves being generally at right angles to the leaf on the main axis. A curious case occurs in Salix cordcUa^ S. lucida, and S. lantita. The inner membranous face of the scale separates more or less completely from the coria- ceous outer one, and resembles a second scale. It is, however, exactly opposite to the outer layer of the scale (not alternate), and is divided in the same way as the outer layer. Perhaps, however, the strongest reason for regard- ing the outer sheath as composed of a pair of leaf- blades is that we often find a pair of buds at the base. Lindley ! quotes this as showing that stipules occasionally develop buds at their base. It seems more reasonable to regard the fact as evidence that they represent leaves, and not merely stipules. It is remarkable that while in the Poplars (Pojpidus) the buds are protected, by the stipules, in Salix the 1 Introd. to Botany, p. 99. i 2 116 BUDS AND STIPULES stipules are minute in the bud, or even absent, and this function is performed mainly by the leaves. The stipules, however, though always very small in bud, and in some species (S. retusa, Grahami, Caprea, repenSj &c.) permanently so, in others become larger, and in some (8. dasyclados, myricoides, &c.) attain a considerable size. Their chief function appears to be to protect the axillary buds, which are also sheltered by the dilated and concave bases of the petioles. That the winter-buds of the Willow should be protected by modi- fied leaves is the more remarkable since some species at least subsequently develop large stipules. Ohlert (17) mentions the Willow among the cases in which there is no terminal bud. At any rate, it appears rarely, if ever, to maintain itself permanently. But, although as a rule it soon perishes, it is formed on the same plan as the lateral buds. VIBURNUM (THE GUELDER ROSE) The winter-buds of the Guelder Rose (Viburnum Opulus), both terminal and lateral (PL II. fig. 1), are oblong-oval, varying considerably in size, according to their situation on the shoots and the strength of the latter. Each bud is covered by two pairs of scales, which are modified petioles bearing just a trace of an undeveloped lamina at the apex. The outer pair of scales are the most modified and cohere by their edges ; they are inserted right and left ON THE STRUCTURE OF BUDS 117 of the axis, and likewise of the leaf in whose axil they occur. They are brownish red, glabrous, shining, and for a time increase in size with the swelling of the buds in spring. Finally, they burst antero-posteriorly along the line of union for a quarter to three-quarters of their length, the greatest amount of fission occurring, as a rule, along the posterior face, allowing the developing axis with its leaves to make its exit at the apex. Each of these scales is keeled, the keel corresponding to the midrib. Three or five veins may be seen on the inner face, corresponding to the principal vascular bundles running through the petiole into the lobes of the lamina. Three of them generally terminate in gland- like tips. The second pair of scales are more membranous, pale green, five-nerved, reticulate, cohering in a tube, which bursts from the apex downwards for one-third to one-half its length, or more, when growth is re- sumed in spring. They double their length during and after the expansion of the buds, and are, therefore, intermediate in character between the most modified pair of scales and the true leaves. The three principal veins terminate in gland-like teeth, thus, possibly, indicating the presence of the lamina in an undeveloped state. When fully developed they are seen to be spathulate by a dilatation of the upper half. If the terminal bud is examined, it will be seen that the scales are opposite decussate, and serially continuous 118 BUDS AND STIPULES with the uppermost pair of leaves that fell in the previous autumn. The young leaves in spring are serially continuous with both the two pairs of scales FIG. 186.— VIBURNUM LANTANA, x 2. FIG. 187. — PAKT OF LEAF OF V. LANTANA, x 75, showing stellate hairs. and the leaves of the previous season. Unless the terminal bud ends in an inflorescence, the shoots of successive years are interrupted only by two pairs of scales. Strong shoots do, as a rule, terminate in an ON THE STRUCTURE OF BUDS 119 inflorescence, and the apex dies, so that growth is resumed by the lateral buds. In the flowering buds the second pair of scales are larger, vase- shaped, and also more deeply divided, es- pecially on one side. Those which bear leaves only are flattened at right angles to the stem. In Viburnum Lantana (Wayfaring Tree) (figs. 186 and 187), on the contrary, the leaves are all normal. The outer ones protect the inner ; but they all develop, and suffer very little from the cold. They are protected by a thick coat of stellate hairs, which cross and intercross, thus forming a sort of grey felt. As the young leaves increase in size these hairs do not appear to increase in number, and they are, consequently, carried further from one another. Fig. 187 is taken from such a bud which had attained a length of rather more than an inch. PROTECTION BY LEAF-STALK In the Elder (Sambucus nigrcb) the scales protecting the bud are petioles. Externally are a pair of very small brown scales ; then a larger pair at right angles ; then a pair much more elongated, greenish, and with more or less developed leaves. In this respect they differ very much ; sometimes there are three small points at the summit, sometimes a well-formed leaf ; and every gradation between the two occurs. The two opposite leaves often differ considerably, and when one 120 BUDS AND STIPULES of the two has its back to the main stem it is often much smaller than the outer one. PROTECTION BY STIPULES In by far the larger number of cases stipules protect Fm. 188. — SHOOT or LEEA COCCINEA. P, petiole of leaf, the lamina being cut off ; S, stipule ; L, young leaf emerging from stipules. the younger leaves only, but in some species they develop early, and cover their own leaf-blades. This is the case, for instance, in the Pea (fig. 26, p. 23) and the Hop (Humulus Lupulus) (figs. 47, 48, p. 34). In the Vine, again, the stipules are large, and appear ON THE STRUCTURE OF BUDS 121 some time before the leaves, covering the whole bud (figs. 127, 128, p. 84). They fall early. FIG. 189.— VIRGINIAN CREEPER. •S7, stipule ; t, tendril. In Leea (Tj. coccinea), another member ot the Vine family, the same thing occurs ; they are also (fig. 188^ large, and enclose the whole bud, but they are persistent. 122 BUDS AND STIPULES In the allied genera, Gissus, and Ampelopsis (Vir- ginian Creeper) (fig. 1 89), the stipules also cover their own leaf-blades. In Bucklandiapopulnea(fig. 190), a Himalayan plant FIG. 190. — SHOOT OF BUCKLANDIA POPULNEA. S, S, stipules ; P, petiole. which belongs to the Hamamelidecs (the Witch Hazel family), the stipules are large, oval, unequal-sided, and cohere at the edges, thus forming an almond-shaped box, within which the leaf is developed. The petiole elon- ON THE STRUCTURE OF BUDS 123 gates greatly, and becomes twice bent, as shown in the figure, so that the leaf remains erect. This arrange- ment is, so far as I know, unique. In the Passion Flower (Passiflora racemosa) the stipules are large, foliaceous, and developed far in advance of their own leaves, so that each pair enclose their own leaf, the simple tendril in its axil, and the younger portion of the bud. Proceeding from the out- side inwards, the stipules change considerably, being first ovate, gradually becoming smaller, then lanceolate, and finally subulate. In some other species of Passi- flora the stipules more or less completely protect the bud, and the petioles are terete, and are provided with glands. In by far the greater number of cases, however, stipules protect the younger leaves only. In the Willows, as we have already seen, the sti- pules develop late, and the bud is protected by a pair of modified leaves. In the allied genus, Populus (the Poplar), on the contrary, the stipules develop early, and to them the protection of the bud is entrusted. In the Black Poplar (Populus nigra) the terminal bud (fig. 191) is conical and somewhat angular. The first arid second pairs of scales (fig. 192), form- ing part of the terminal bud, are stipules belonging to leaves that developed during the previous summer and fell in autumn. They only cover, however, a part of the bud. They are the hardest of the 194 1 198 197 POPULUS NIGRA, VAR. PYRAMIDALIS, X 2. WlNTER-BUDS. PIG. 191. — Terminal bud showing one pair of persistent stipules, st, st, belonging to a leaf of a previous season. PIG. 192. — Terminal bud snowing one from each of two pairs of persistent stipules, st', st". FIG. 193. — Axillary bud showing only one of the outer pair of stipules, st. FIG. 194. — I, third leaf in the bud, often dying in winter ; st, st, its stipules shown separately above. FIG. 195.— I, fifth leaf in the bud ; st,st,its stipules. FIG. 196. — The same shown separately. FIG. 197.— I, eighth leaf in the bud ; st, it, its stipules. FIG. 198. — I, outer face of eighth leaf ; st, st, its stipules spread out. ON THE STRUCTURE OF BUDS 125 stipules, because they are dead. The third pair are larger, and to them belongs the first leaf of the bud (fig. 194). The fourth pair are longer than the third. Their leaf-blade is subulate, and about one-third as long as their stipules. Sometimes it dies in winter. The fifth pair are sometimes nearly as long as the bud. The third leaf-blade belongs to them, and is consider- ably larger, though but slightly longer. The fourth leaf- blade is nearly as long as its stipules. The seventh pair are about half the length of their leaf- blade, and thin. The ninth and tenth pairs are less than half the length of their leaf-blade. This represents the average composition of a bud at midwinter; but there is considerable variation in the relative lengths of the leaves and their stipules. Sometimes the third leaf belonging to the fifth pair ol stipules is nearly equal in length to the latter, but it may be the fourth, fifth, or sixth leaf which attains this size. The first two or three leaves never attain any great size, even if they live through the winter. Their stipules, however, are always largely developed, and more or less cemented together with a viscid gum, obviously for the protection of the leaves. The leaves that attain a large size in the bud retain their pre- dominance after expansion, while the small outer ones remain relatively small. The axillary buds are smaller and somewhat dit- ferently constructed. The outer covering is short, broad, 126 BUDS AND STIPULES and open on the side towards the stem ; the second is longer, and narrower in proportion. Several of the species secrete a gum, which forms an additional protection to the bud. THE LIME (Tilia) In the Lime (Tilia vulgaris) (PL I. fig. 1) the pseudo-terminal and lateral buds are very similar. They are generally lop-sided or tumid on one side, owing to the thickening of the small outer scale, particularly along the midrib. The true apex of the shoot becomes disarticulated and falls off. The bud does not lie opposite the centre of the leaf, but a little 011 one side. As already mentioned (ante, p. 9), this occurs in other trees, as, for instance, in the Beech and Hornbeam (fig. 11). The consequence is that the pseudo-terminal bud has a scar on each side of it — one that of its leaf, the other that of the fallen shoot. The scales of the winter-bud are arranged on alternate sides of the bud, the leaves being alternate and distichous. The outer scale overlaps the second at the base, but is little more than half its size, though two-thirds the length of the bud. The first two are coriaceous, glabrous, and not accompanied by a leaf; they are also obtusely and slightly carinate. Some- times one stipule of the outer pair is absent. The next two are larger, more nearly equal in size, roundly cordate, showing an inclination to ON THE STRUCTURE OF BUDS 127 become petiolate owing to their being much wider than their insertion. They are glabrous, as long as the bud, rolled round three-fourths of it, the outer one covering the same extent as the inner, which is more membranous, except at the tip. They are accompanied by a small, conduplicate, silky leaf. The next pair are broadly elliptic, unequal, mem- branous, and more or less silky on both surfaces. The larger scale or stipule is always the outer of the pair. The second leaf is much larger than the first, densely silky, with unequal parts, the narrower one being uppermost. The edges of the leaf are always directed under the larger stipule ; and it will be noted that the direction of the leaf and the larger of each pair of stipules are altered in each succeeding set. This is due to the alternate and distichous arrangement of the leaves. The fourth pair are oblong-elliptic, covering three- fourths of the bud, as in succeeding cases, and more silky than the previous pair on the outer face, but otherwise similar. The leaf is as long as the next younger pair of stipules, and lies in a convex manner over them. The fifth pair are oblong, and the outer stipule covers less tlian half of its fellow. The sixth pair are more unequal and very much smaller. The seventh pair are oblong-lanceolate and very small ; while the eighth pair are still smaller and membranous. 128 BUDS AND STIPULES The next younger leaf in each case lies beneath its own stipules, and in that position corresponds to the opening left uncovered by the previous and older pair. None of the pairs of stipules completely surround the bud. The outer scales are often of a rich crimson (PI. I. figs. 1, 2), and the next few sometimes of a brilliant ruby with greenish tips. When the buds first open the leaves, as is the case in other trees — for instance, the Beech, Hornbeam, Elm. &c. — turn downwards, as- suming, as Mr. Henslow has pointed out, the attitude of some leaves when asleep, and probably for the same reason, namely, to expose a less surface to the sky during the cold nights of spring. THE BIRCH (Betula alba) In the Birch also the terminal shoot perishes, and the apparently terminal bud is really axil- lary. If an apparently terminal bud is carefully examined in winter it shows four scars at the base. Two ot these are large, and are those left by the death of the terminal shoot and the leaf respectively. The two smaller ones, which are not always easy to see, are those of the stipules of the fallen leaf. The bud itself is ovoid-oblong, obtuse, glabrous, or with a few cilia at the margins of the scales, and deep ON THE STRUCTURE OF J5UDS 129 brown. The outer scales represent stipules the leaf- blades of which are not developed. The first pair are slightly unequal in length, and do not overlap at any point nor surround the whole of the bud. The second pair, when spread out, are almost semi- orbicular, rounded at the apex, and slightly unequal in length, the inner one being the longer and over- lapped at the base by its fellow at both edges. They cover a considerable portion of the bud, owing to their width. The third pair are as long as the bud, covering the whole of the younger members and over- lapping at their edges. They are more membranous than either of the one or two preceding pairs, and are more or less covered with a viscid gum. They are also slightly narrowed at the base. The fourth pair are more decidedly boat-shaped than the previous one, but are still imbricate. The first leaf generally occurs in connection with the third or fourth pair -of stipules, but inside of, and covered by, them. It is rhomboid, acute, shortly petiolate, serrate, thinly pube- scent, glandular, viscid, and concave. The fifth pair are somewhat smaller than the fourth, but otherwise similar, as is their leaf. The latter is much more involute in bud, though neither strictly convolute nor conduplicate. Its form is doubtless due to the abrupt arrest of the younger members of the bud ; for the fourth and fifth pairs of stipules, together vvith the first and second leaf belonging to them re- 130 BUDS AND STIPULES spectively, are greatly in advance of those that follow. The sixth pair of stipules and the younger members of the bud they enclose will show a reason for the second leaf being partly involute, so as to occupy the space. According to Henry (18, 309), the outer scales are the stipules of the last leaves of the previous year. The description given above, however, is, I believe, the correct one. THE BEECH (Fagus sylvatica) The bud of the Beech (figs. 199-210) is more complicated. It is elongated, spindle-shaped, half to three-quarters of an inch in length; on the outside are four closely imbricating rows of stipules, arranged apparently in opposite decussate pairs. I say appa- rently, because, as the leaves are alternate, it is pos- sible that each pair of these stipules are really alternate, though so compressed as to appear to be opposite. The first pair (fig. 200) are small, triangular, and pointed. The five following are also triangular, each rather larger than the preceding and more convolute, till they almost enclose the upper part of the bud. The lower ones are brown and coriaceous ; the upper membranous, and furnished with numerous straight, longitudinal, parallel, slender veins running from the base to the apex. The covered parts are white, the exposed brown. The upper ones are fringed with long, FIG. 207. / st FIG. 208. sc.st FIG. 210. THE BEECH (Fagus sylvatica). FIG. 199.— Winter-bud. FIG. 200.— First or lowest pair of stipules. FIG. 201.— Sixth pair of stipules overlapping at the corners. FIG. 202.— Eleventh pair of stipules, showing how one is rolled within the other ; Z, position where the leaf should be, though it is yet absent. FIG. 203.— Diagrammatic trans- verse section of the stipules, showing the extent to which they overlap. FIG. 204.— The bud after eleven pairs of stipules have been removed ; Z, the first leaf : st, st, the twelfth pair of stipules ; e, e, the edges of the outer one of the twelfth pair. FIG. 205.— it, st, the twelfth pair of stipules flattened put ; /, the first leaf belonging to the same. . FIG. 206. — st, st, the thirteenth pair of stipules : Z, the second leaf. FIG. 207. — st, st, the fourteenth pair of stipules ; Z, the third leaf. FIG. 208. — .