CHAPTER IV. 



SHOOTS. 



40. General characters. — The term shoot is used to include 

 both stem and leaves. Among the lower plants, such as 

 the algae and toadstools, there is no distinct stem and leaf. 

 In such plants the working body is spoken of as the thallus, 

 which does the work done by both stem and leaf in the 

 higher plants. These two kinds of work are separated in 

 the higher plants, and the shoot is differentiated into stem 

 and leaves. 



41. Life-relation. — In seeking to discover the essential 

 life-relation of the stem, it is evident that it is not neces- 

 sarily a light-relation, as in the case of the foliage leaf, 

 for many stems are subterranean. Also, in general, the 

 stem is not an expanded organ, as is the ordinary foli- 

 age leaf. This indicates that whatever may be its essential 

 life-relation it has little to do with exposure of surface. 

 It becomes plain that the stem is the great leaf-bearing 

 organ, and that its life-relation is a leaf-relation. Often 

 stems branch, and this increases their power of producing 

 leaves. 



In classifying stems, therefore, it seems natural to use 

 the kind of leaves they bear. From this standpoint there 

 are three prominent kinds of stems : (1) those bearing foli- 

 age leaves ; (2) those bearing scale leaves ; and (3) those 

 bearing floral leaves. There are some peculiar forms of 

 stems which do not bear leaves of any kind, but they need 

 not be included in this general view. 



