THE LEAF 



47 



conduplicate leaves wholly or partially enclose each 

 other; and (4) half-equitant, where two condupli- 

 cate leaves enclose each other by half their blades. 

 These arrangements are seen to best advantage 

 mostly in flower- buds, and will therefore be illus- 

 trated with examples in a subsequent chapter. 



Leaves are ordinarily flat expanded structures with 

 an upper and an under surface, the former being of a 

 deeper green than the latter. Such leaves are there- 

 fore called DORSi-VENTRAL. But leaves like those of 

 Onion are more or less round, vertical, and equally 

 green all round ; such leaves are said to be centric. 



In plants like Aloe or ghrita-kumari, Agave or 

 belati-anaras (see fig. 258), murga (Sansevieria Rox- 

 burghiana), Pineapple or anaras, a cluster of leaves 

 seems to arise from the top of the root, as if the plants 

 have no stems. As a matter of fact, in such plants the 

 stem forms as it were a short thick crown of the root, 

 on which the leaves are closely inserted. Such leaves 

 are said to be radical leaves as opposed to cauline 

 LEAVES, which are attached on the elongated stems 

 or their branches. 



CHAPTER Vlil 



THE LEAF (Continued) 



We have already learned that leaves originate 

 laterally from the stem in an acropetal order, so that 

 the youngest leaf is nearest the apex of the stem and 

 the oldest leaf nearest the base of the stem. They are 

 usually arranged on the stem either spirally or in 

 WHORLS. The arrangement is said to be spiral when 



