CHAPTER IV 



SHOOTS 



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

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

 the alga? and toadstools, there is no distinct stem and leaf. 

 In such plants the working body is spoken of as tlu- tliallus, 

 which does the work clone by botli 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 leares. 



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

 life-relation of tlie stem, it is evident tliat it is not neces- 

 sarily a liglit-relatiou, as in the case of tlie foliage leaf, 

 for man}' stems are subterranean. Also, in general, tlie 

 stem is not an expanded organ, as is the ordinai'y foli- 

 age leaf. Tliis indicates tliat whatever may be its essential 

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

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

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

 stems branch, and tliis increases tlieir 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) tliose bearing foli- 

 age leaves ; (3) those bearing scaly leaves ; and (3) those 

 bearing iioral leaves. There are some peculiar forms of 

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



not be included in this general view. 



53 



