106,107.] TRANSFORMATIONS OF THE LEAF. 125 



an IDEA of the Divine Architect, whence is derived 

 the form of every other appendage of the plant. To 

 trace out this idea in all the disguises under which it 

 lurks, is one of the first aims of the botanist. Several 

 of these forms of disguise have already been noticed 

 for example : 



319. The scales which clothe the various forms of 

 scale-bearing stems are leaves, or more usually petioles, 

 reduced and distorted, perhaps by the straitened cir- 

 cumstances of their underground growth. The scales 

 of corms and rhizomes are mostly mere membranes, 

 while those of the bulb are fleshy, serving as deposi- 

 tories of food for the future use of the plant. That 

 these scales are leaves is evident 1st, from their po- 

 sition at the nodes of the stem ; 2d, from their occa- 

 sional development into true leaves. Of the same 

 nature are the brown scales of Winter buds. 



320. The cotyledons of seeds or seed-lobes are 

 readily recognized as leaves, especially when they arise 

 above-ground in germination, and form the first pair 

 upon the young plant ; as in the Beechnut and Squash 

 seed. Their deformity is due to the starchy deposits 

 with which they are crammed for the nourishment of 

 the embryo when germinating, and also to the way in 

 which they are packed in the seed. 



321. Phyllodia are certain leaf-forms, consisting of 

 petioles excessively compressed, or expanded vertically 

 into margins, while the true lamina is partly or en- 

 tirely suppressed. Fine examples are seen in our 

 greenhouse Acacias from Australia. Their vertical 

 or edgewise position readily distinguishes them from 

 true leaves. 



322. Ascidia, or pitchers, are surprising forms of 



