AS BUD-SCALES, TENDKILS, SPIKES, KTC. 



1C7 



double purpose, being not only organs for assimilation, — the general 

 office of foliage, — but also repositories in which 

 assimilated matter is stored up, just as in the root 

 of the Beet and Radish (Fig. 138), or in subter- 

 ranean stems or branches in rootstocks, tubers, 

 and corms ( 188 - 190, 194). The bases of those 

 leaves which form the scales of bulbs (191) are 

 turned to the same use. In Fig. 176 we have a 

 leaf the blade of which acts as foliage in the ordi- 

 nary manner of leaves, while its subterranean 

 thickened base serves as a repository of nutri- 

 ment which the blade has elaborated. The very 

 first leaves of the plant, viz. the cotyledons or 

 seed-leaves (120-123) are commonly subservi- 

 ent to this purpose, and some- 

 . i/L __ times to no other, as in the 



Pea, Horsechestnut, Oak, &c. 

 (124), where these leaves are mere repositories 

 of food for the use of the germinating plant. 



298. Leaves as Bud-scales, &c. (161) exhibit the 



same organ under a different modification, and 

 subserving a different special purpose. Of the 

 same nature are the degenerated or abortive 

 y^Hni scale-like leaves on the vernal stems of peren- 



/ ' 1 nial herbs near or beneath the surface of the 



ground, and on Asparagus shoots, and also those 

 scales which colored parasitic plants produce in 

 place of foliage (1;32). The primary leaves of 

 Pines are all thin and dry bud-scales ; the actual 

 foliage originating from a branch in the axil of 

 each (Fig. 212). 



299. Leaves as Tendrils are seen in the proper 

 Pea tribe ; where however only the extremity 

 of the common petiole is transformed in this 



295 manner (Fig. 287, 289) ; but in one plant 



of the kind (Lathyrus Aphaca) the whole leaf becomes a tendril. 

 300. Leaves as SpillCS occur in several plants. The primary leaves 



PIG. 295. A twig of American Arbor Vitu?, exhibiting both awl-shaped and scale-shaped 

 leaves 



FIG 296. A summer shoot of the Barberry, showing a lower leaf in the normal state ; the 

 Bext partially, those still higher completely, transformed into spines. 



