38 BOTANY part i 



stems arising from such subterranean shoots the formation of similar 

 scale leaves generally precedes the development of the foliage leaves, 

 with which they are connected by a series of transitional forms. 



Braeteal Leaves i-esemble scale leaves in form, and have a similar 

 origin (Fig. 34 hh). They act as subtending leaves for the floral 

 shoots, and are termed BRACTS. They are connected with foliage 

 leaves by intermediate forms (Fig. 38). Though they are not in- 

 frequently green they may be otherwise coloured, or even colourless. 



Floral Leaves. — The modified leaves which form the flowers of 

 Phanerogams are termed floral leaves. In the highest development 

 attained by a phanerogamic flower (Fig. 39), the successive floral leaves 

 are distinguished as sepals {k), petals (c), stamens ((f), and carpels (r/). 

 In form the sepals and petals approach the bracts. In most cases the 

 sepals are green and of a firm structure ; the petals, on the other hand, 

 are more delicate and variously coloured. In some cases, as in the 

 Christmas Rose (EeHehorus) and the Monkshood (Aconitum) (Fig. 563), 

 the petals are transformed into tubular nectaries and modified in 

 accordance with this. The stamens are generally filamentous in shape, 

 and produce the pollen in special receptacles. The carpels in Angio- 

 sperms by closing together form receptacles within which the ovules 

 are produced. The stamens and carpels of Phanerogams correspond 

 to the spore-bearing leaves of the Vascular Cryptogams. Such spore- 

 bearing leaves are termed SPOROPHYLLS, and even in the Vascular 

 Cryptogams exhibit a greater or less departure from the form of other 

 foliage leaves. 



It is evident that the scale and braeteal leaves are to be considered as rndi- 

 nientary foliage leaves, not only from the mode of their development bnt also from 

 the possibility of transforming them into foliage leaves. Goebel, by removing 

 the growing tip and foliage leaves of a shoot, succeeded in forcing it to develop 

 other foliage leaves from its scale leaves C"'"). Rhizomes, grown in the light, 

 develop foliage leaves in place of the usual scale leaves, and even on a potato it is 

 possible to induce the formation of small foliage leaves instead of tlie customary 

 scale leaves. 



Leaf Sears. — After a leaf has fallen, its previous point of 

 insertion on the stem is marked by the cicatrix or scar left by the 

 fallen leaf. In winter, accordingly, when the trees have shed their 

 leaves, the axillary buds are seen to be situated above the leaf-scars. 



Vernation and Aestivation.^ — A section through a winter bud 

 shows a wonderful adaptation of the young leaves to the narrow 

 space in which they are confined. They may be so disposed that 

 the separate leaves are spread out flat, but more frequently they 

 are folded, rolled (Fig. 40 /), or crumpled. The manner in which 



' [The use of tliese terms in tlie fiillowiiijj; paragraph differs from that customary in 

 Kngland. Hy vebnation is understood the arrangement of tlie leaves in a vegetative 

 bud as a whole. The folding of eacli individual leaf in the bud is termed ptyxis. The 

 term AESTIVATION is api)lied to tlie arrangemeut of the jiarts in a flower-bud. — Trans.] 



