LEAVES, 



[section 7. 



uame of Smilaxj is peculiar aud puzzling. If these blades (Fig. 167, 168) 

 are really leaves, they are most auoinalous iu occupying the axil of another 

 leaf, reduced to a little scale. Yet they have an upper and lower face, as 

 leaves should, although tiiey soou twist, so as to stand more or less edge- 

 wise. If they are branches wiiich have assumed exactly the form aud 

 office of leaveSj they are equally extraordiuary iu not making any further 

 development. But in lluscus, flowers are borue on one face, in the axil 

 of a little scale : aud this would seem to settle that they are branches. In 

 Asparagus just the same things as to position are thread-shaped aud 

 branch-like. 



§ 2. LEAVES OF SPECIAL CONFORMATION AND USE. 



165. Leaves for Storage. A leaf may at the same time serve botb 

 ordinary and special uses. Thus in those leaves of Lilies, such as the 

 common White Lily, which sprmg from the bulb, the upper and green part 



serves for foliage 

 and elaborates 

 nourisliment, while 

 tlie thickened por- 

 tiou or bud-scale 

 beneath serves for 

 the storage of this 

 nourishment. The 

 thread-shaped leaf 

 of the Onion ful- 

 •fils t he same office, 

 and the uourishiug 

 matter it prepares 

 is deposited iu 

 its sheathing base, 

 forming ( nc of the 

 concentric layers of 

 the onion. When 

 these layers, so thick aiid succulent, have given up their store to the grow- 

 ing parts within, they are left as thin and dry husks. In a Houseleek, 

 an Aloe or an Agave, the green color of the surface of the flcsiiy leaf indi- 

 cates that it is doing the work of foliage; the deeper-seated white por- 

 tion within is the storehouse of the nourishment which the green surface 

 has elaborated. So, also, the seed-leaves or cotyledons arc commonly used 

 for storage. Some, as iu one of the Maples, the Pea, Horse-chestnut, 

 Oak, etc., are for notiiing else. Others, as in Beech and iu our commou 



Fig. 169- A young Agave Americana, or Century-plant; fleshy-leaved. 



