THE SHOOT. 8 1 



Leaves themselves may be developed as tendrils or as thorns, so that 

 it must not be assumed from appearance alone that such members are 

 forms of the shoot, Observation of the origin and relation of the mem- 

 bers will reveal their true nature. If shoots, they will usually be sub- 

 tended by a leaf ; if leaves, they will often have a bud or a shoot in their 

 axils. Thorns or tendrils which do not arise at the nodes are reckoned 

 as shoots. 



101, Duration. — Shoots are either annual, biennial, or 

 perennial. If the entire shoot dies this generally involves 

 the death of the whole plant, though new adventitious shoots 



Fig. 70.— Shoots of Vella spinosa, showing thorns. Natural size.— After Kemer. 



may arise from the roots, as in sweet potatoes. In many 

 plants, in which the shoot seems to die at the close of the 

 growing season, an underground portion really survives, and 

 sends up the new shoots. Such plants, if they live for two 

 years, are called biennials ; or, if they live for several or 

 many years, are called perennials. 



The shoot may be composed mainly of soft tissues, and 

 persist underground, where it is protected against unfavorable 

 conditions, such as drought and cold, and especially against 



