STEM. 



[chap. 



The root frequently becomes much thickened in perennial 

 and biennial herbaceous plants, serving as a reservoir of 

 nourishment for the growth of the sprouts of the following 

 season. When the branches or fibres of a root become 

 thickened in this way, the root is said to be tuberous. Such 

 tuberous roots much resemble certain forms of underground 

 and similarly thickened stems, but differ from them in the 

 absence of leaf-buds. Potatoes and Onions are called 

 ro(its, but we shall presently show that this is a misnomer. 



Fig. 44. Cycns revoluta. The stem [caudex] unbranched. 



3. The Stem always originates in a bud ; the primary stem 

 of the plant from the bud of the embryo— the plumule. 

 Branches in like manner originate in similar buds formed 

 in the axils of leaves. Buds borne in the axils of leaves 

 are axillary; those which terminate a stem or branch, 

 and which, after a winter's rest in cold climates, renew the 

 shoot, are tenniiial. Some trees, as Palms and Cycads, never 

 or rarely develope any other than a terminal leafy bud, 



