THE PLANT BODY. 219 



From still another standpoint they might be studied as indi- 

 cating relationships. Their form, position, arrangement, etc., 

 serve to characterize certain groups of individuals so that they 

 can be distinguished from others. 



The different forms of the members are usually designated by 

 special names, but it is convenient to group them in the single 

 series. 



360. Stem Series. 



Tubers, underground thickened stems, bearing buds and scale 

 leaves; ex., Irish potato. 



Root-stocks, underground, usually elongated, bearing scales 

 or bracts, and a leafy shoot; ex., trillium, mandrake, etc. 

 Root-stocks of the ferns bear expanded, green leaves. 



Runners, slender, trailing, bearing bracts, and leafy stems as 

 branches; ex., strawberry vines. 



Corms, underground, short, thick, leaf bearing and scale 

 bearing; ex., Indian turnip. 



Bulbs, usually underground, short, conic, leaf and scale bear- 

 ing; ex., lily. 



Thorns, stout, thick, poorly developed branches with rudi- 

 ments of leaves (scales); ex., hawthorn. 



Tendrils, slender reduced stems. 



Flower axes (see morphology of the angiosperms). 



361. Leaf series. — Besides the foliage leaves, the following 

 are some of their modifications : 



Flower parts (see morphology of the angiosperms). 



Brads and scales, small, the former usually green (flower 

 bracts), the latter usually chlorophylless. Bud scales are some- 

 times green. 



Tendrils, modifications of the entire leaf (tendrils of the 

 squash where the branched tendril shows the principal veins of 

 the leaf), modification of the terminal pinnse of the leaf (vetch), 

 etc. 



Spines (examples are found in the cacti, where the stem is 

 enlarged and green, functioning as a leaf). 



