52 SUNFLOWER. [CH. IV 



that the section also bisects a leaf and leaf-stalk longi- 

 tudinally, it will be seen that in the acute angle between 

 the leaf-stalk and the stem, i.e. just above the insertion of 

 the leaf, is a bud, similar in character to the small bud 

 which lay between the cotyledons and gave origin to the 

 main stem. This bud which, if it developes, will grow out 

 into a branch bearing leaves in its turn, is called axillary, 

 from its position in the axil, or armpit-like angle above 

 the leaf (see fig. 21), and it is a fact of broad general 

 significance that normal branches always spring from the 

 axil of a leaf. This general law is useful in understanding 

 the structure of certain plants : of this the potato- and the 

 artichoke-tuber have already supplied instances, for the 

 eyes or buds grow in the axils of leaves whose traces are 

 visible in the markings on the surface of the tubers. It 

 makes it possible also to understand such a plant as the 

 Butcher's Broom (Ruscus aculeatus). Here the observer 

 sees the stem beset with flat green outgrowths, which 

 he naturally takes for leaves, until a closer examination 

 shows him that each outgrowth springs from the axil 

 of a scale-like rudimentary leaf. This observation points 

 to what is the truth, namely, that the outgrowths are 

 flattened branches functioning as leaves, and taking the 

 place physiologically of the useless but true leaves in 

 whose axils they grow. 



Although it is not always possible to tell a leaf 

 from a branch by its appearance, there are nevertheless 

 some characters by which the two can be distinguished. 

 In the first place, leaves differ from branches in the 

 limited character of their growth. A leaf soon ceases to 



