24 



ELEMENTARY BOTANY. 



in the case of the Pumpkin and certain other plants, some 

 time after germination it will be found that they have changed 

 their shape somewhat and become green, like ordinary leaves. 

 As a rule, however, the cotyledons change but little, and simply 

 furnish the nourishment for the plantlet during germination. 

 In the bulb-scales is stored up food for the early growth of the 

 plant the following season. This nourishment is consumed 

 in such bulbous plants as the Hyacinth, etc., by the produc- 

 tion of flowers early in the season, or in advance of the leaves. 



3. The leaves of underground stems are generally reduced 

 to mere scales. The Bud-scales, which protect the tender 

 parts within, are modified leaves. A gradual transition be- 

 tween them and the first foliage leaves may often be traced, 

 as in the Lilac, Hickory, etc. When spines occupy the place 

 of leaves, they are modified forms of the latter. In the Bar- 

 berry all gradations may be seen on a single shoot. The leaf, 

 or a portion of it, may become changed into a tendril for 

 climbing, as in the Pea, Vetch, etc. (Fig. 3.) 



4. Very interesting modifications of leaves are furnished by 



Fig. 3. 



Fig. 4. 



the Pitcher-plant {Sarracenia), Sundew {Drosera), and Ve- 

 nus's Fly-trap (Dioncea). The leaves of Sarracenia are hollow 

 cups or tubes (Fig. 4) inwardly covered with hairs directed 



