CHAPTER V 



THE STEM AND THE LEAF 



FIG. 37. Beefwood, Casuanna, an Austra- 

 lian switch plant destitute of foliage leaves 

 and depending on the chlorophyll-containing 

 cells of the bark for photosynthesis 



Photograph by Robert Cameron 

 66 



55. Work of the leafy 

 shoot. How plant food 

 is made from raw mate- 

 rials has been briefly ex- 

 plained in Chapter IV. 

 In almost all of the 

 higher plants this food- 

 making is carried on 

 by the cooperation of 

 the stem and the leaf. 

 Taken together, they 

 are known as the shoot, 

 so that the parts of a 

 flowering plant (before 

 it begins to flower) are 

 root and shoot. 



56. Photosynthesis in 

 the stem. Among seed 

 plants in general it is 

 the leaves that do by 

 far the greater part of 

 the work of photosyn- 

 thesis, but some plants, 

 as the cacti (fig. 66), 

 are practically leafless 1 



1 That is, they have no 

 leaves which can do any 

 food-making or which at all 

 resemble ordinary leaves. 



