50 



MORPHOLOGY OF LEAVES. 



[LESSON 7. 



seed (Fig. 11), Beech (Fig. 13-15), the Bean and Pea (Fig. 16- 

 20), the Oak (Fig. 21, 22), and Horsechestnut (Fig. 23, 24) ; where 

 the food upon which the plantlet feeds when it springs from the 

 seed is stored up in its cotyledons or first leaves. And we have 

 noticed how very unlike foliage such leaves are. Yet in some cases, 



as in the Pumpkin (Fig. 10), they 

 actually grow into green leaves as 

 they get rid of their burden. 



121. Bulb-Scales (Fig. 73-75) of- 

 fer another instance, which we were 

 considering at the close of the last 

 Lesson. Here a part of the nourish- 

 ment prepared in the foliage of one 

 year is stored up in the scales, or 

 subterranean thickened leaves, for the 

 early growth and flowering of the next 

 year ; and this enables the flowers to 

 appear before the leaves, or as soon 

 as they do ; as in Hyacinths, Snow- 

 drops, and many bulbous plants. 



122. Leaves as Bud-scales, c, True 

 to its nature, the stem produces 

 leaves even under ground, where 

 they cannot serve as foliage, and 

 where often, as on rootstocks and 

 tubers (97 - 103), they are not of 

 any use that w r e know of. In such 

 cases they usually appear as thin 

 scales. So the first leaves of the 

 stems of herbs, as they sprout from 

 the ground, are generally mere scales, 

 such as those of an Asparagus shoot ; 

 and such are the first leaves on the 

 stem of the seedling Oak (Fig. 22) 

 and the Pea (Fig. 20). Similar 

 scales, however, often serve an im- 

 portant purpose ; as when they form the covering of buds, where 

 they protect the tender parts within (44). That bud-scales are 



PIG. 77. Leaves of a dnveloping bud of the Low Sweet Buckeye (jEsculus parviflora), 

 showing a nearly complete set of gradations from a scale to a compound leaf of five leaflets. 



