NUTRITION; MEMBERS PLANT BODY. 



73 



applied to the plant body of all the lower plants, the algse and fungi. The 

 algse and fungi together are sometimes called the thallophytes, or thallus 



plants. The word thallus is also sometimes 

 applied to the flattened body of the liver- 

 worts. In the foliose liverworts and mosses 

 there is an axis with leaf-like expansions. 

 These are believed by some to represent 

 true stems and leaves, by others to represent 

 a flattened thallus in which the margins are 

 deeply and regularly divided, or in which 

 the expansion has only taken place at regular 

 intervals. 



Fig. 63. 

 Foliose liverwort ^Bazzania) showing dichotomous branching and overlapping leaves. 



172. Members of the plant body. — In the higher plants there is usually 

 great differentiation of the plant body, though in many forms, as in the duck- 

 weeds, it is a frond. While there is great variation in the form and func- 

 tion of the members of the plant body, they are reducible to a few fundamental 

 members. Some reduce these forms to three, the root, stem, and leaf, while 

 others to two, the root and shoot, which is perhaps the better arrangement. 

 Here the shoot is farther divided into stem and leaf, the leaf being a lateral 

 outgrowth of the stem. The different forms of the members are usually des- 

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

 series. Examples are as follows: 



173. 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., In- 

 dian turnip. 



