12.] CHAPTER II. SPECIAL MORPHOLOGY OF THE MEMBERS. 



59 



have remained in a rudimentary condition. They always occur 

 on subterranean stems {e.g. the scales of the Onion, see also Figs. 

 22 and 23 n), and sometimes on aerial stems. Many plants which 

 are not green (Orobanche, Neottia) produce only cataphyllary 

 leaves in addition to the floral leaves. The most common form in 

 which they occur upon aerial stems is that of scales investing the 

 buds of trees. In this case they are the lowest leaf-structures 

 borne by the annual shoot, and usually fall off as the bud developes. 

 Some few indigenous trees have naked buds without scales, as 

 Viburnum Lantana, Cornus sanguined, Rhamnns Frangula; their 

 buds are protected by a dense growth of hairs. 



The following varieties of bud- scales may be 

 distinguished : 



a. The bud- scales are tbe stipules of leaves 

 which develope a lamina ; as in Alnus, Lirioden- 

 dron, Marattiaceee. 



b. The bud-scales are the stipules of leaves 

 which develope no lamina : Oak, Beech. 



c. The bud-scales are leaf-bases, the lamina 

 not being developed : Maple, Ash, Horse-Chestnut, 

 Prunus Padus. 



d. The bud-scales are laminae or epipodia : 

 Lilac, Privet, Abietineae. 



In tbe last case the bud-scales may be caused to 

 develope into foliage-leaves by cutting off the top 

 of the branch, or removing its leaves, at the time 

 when the bud-scales are developing. 



Cataphyllary leaves are sometimes 

 thickened so as to serve as depositories 

 for nutritive substances, as in the bulbs 

 of the Onion, Lily, etc. 



5. Bracts and Floral Leaves (Hypso- 

 phylls and Sporophylls ; Fig. 36 H) . These 

 leaves are generally peculiar in form, texture, and colour; their 

 morphology is discussed in connexion with that of the reproduc- 

 tive organs in 16, p. 76, as also in Part III. 



Vernation and Prefoliation. The forms of young leaves and 

 their relative position in the bud, that is their vernation and 

 prefoliation (cestivation and prefioration of floral leaves), require 

 special consideration. 



The vernation (or (estivation) is said to be plane when the leaf is not folded 

 at all ; it is conduplicate when the two halves of the leaf are folded inwards 



Fio. 38. Leaf-spines of Ber- 

 beris vulgaris, at the base of a 

 shoot of one year's growth, 

 a Leaf-spine with broad sur- 

 face ; b with a smaller surface ; 

 1: Ic axillary buds (nat. size). , 



