THE AMERICAN BOTANIST. 45 



leaves persist some time after the flower season, but like 

 man}' other vernal flowering plants, die down earl}' in the 

 summer. 



Urbanii, Illinois. 



BOTANY FOR BEGINNERS— \l. 



MODIFICATIONS OF THE LEAVES. 



If asked to define a leaf, most people would say that it 

 is aflat green affair growing from the stem of a plant. In 

 ordinary cases this might be sufficient but there are many 

 leaves that are neither green nor flat, while all the flat 

 green expansions of the stem are not leaves. 



One of the most curious of the leaves that are not flat 

 is found in the common pitcher-plant (Sarracenia) which 

 is to be found in almost every sphagnum bog. In this case 

 the leaves are hollow cylinders filled with water for the 

 purpose of drowning unwary insects whose decaying 

 bodies will thus afford food for the plant. In this leaf the 

 hollow part is regarded as representing the petiole, w^hile 

 the free portion around the mouth of the well represents 

 the blade. In some of the exotic pitcher-plants especially 

 the genus Nepenthes there is a sessile leaf, beyond which 

 the midrib projects as a coiling tendril and at the tip of 

 this is a small pitcher. Here the leaf is a fly-trap, foliage- 

 leaf and tendril all in one. The sundew's leaves are more 

 like ordinar}^ leaves but thc}^ also act as fly-traps, secret- 

 ing a glistening sticky fluid which holds fast any insect 

 that ma\^ touch them while the leaf margins slowly enfolds 

 and digests it. 



In these instances it is easy to see that the structures 

 for insect catching are modified leaves, but there are other 

 forms of leaves in which their identity is not so plain. For 

 instances, bud scales are but leaves dwarfed for a special 

 purpose and many plants show this by developing the 

 inner bud scales into leaf-like organs in spring. The sharp 

 spines of the barberry are transformed leaves and so are 

 said to be the tendrils of the grape though these latter are 

 perhaps of the nature of stems. In the pea one may see 



