40 Elementary Work in Botany. 



four. This fact should be kept constantly in view 

 by the student. It is the key which opens the way to a 

 clear understanding of all that is most interesting and won- 

 derful in the structure and behavior of plants. 



Whenever it becomes necessary for the good of a plant 

 that something should be done different from the normal 

 work of its primary organs one of these fits itself, as it were, 

 for the new office. Some time in the course of the life of 

 any seed-producing plant one or more of its buds develops 

 into a flower or a cluster of flowers, the parts of which are 

 modified stem and leaves. In a few plants some of the buds 

 become tendrils, the undeveloped leaves remaining useless 

 bracts, or disappearing. In others the leaves, or parts 

 of them, form tendrils (Fig. 48), or, remaining nearly 

 normal, as in nasturtium, clematis, and the jasmine-like 

 solanum, do the work of tendrils. When it is necessary to 

 store up food for the renewal of life after a season of leafless 

 rest, or to carry the plant through a period of drought, 

 stems or leaves become storage organs. In some plants 

 branches burrow in the ground and become tubers (Fig. 33). 

 In others, the base of the stem, consisting of many short 

 nodes, becomes a fleshy rootstock or corm, or, developing only 

 the leaves of the base, a bulb is formed (Fig. 36). Besides 

 these there are many less common but often very useful 

 organs. Bring for the next exercise a potato. 



EXERCISE 28. 



Storage Stems. Study of a Potato. Find the stem end 

 of the potato. The other end is the apex. Can you make 



