294 PHYLU.M XIV. ANTHOPHYTA 



and continue to be so throughout the life of the plant. 

 In the first two the vascular bundles of the leaves are 

 irregularly netted with one another, while in the Water 

 Plantain the bundles are quite as markedly parallel. 

 Also in the stems of the first two there is a more or less 

 cylindrical arrangement of the vascular bundles, showing 

 as a ring in a cross-section, while in the Water Plantain 

 the bundles show little if any cylindrical arrange- 

 ment, the bundles being more or less scattered through- 

 out the cross-section. 



531. These differences are pretty constant for the 

 plants related to Buttercups, Strawberries and Water 

 Plantains respectively, so that botanists have been 

 led to use them for the division of the Flowering Plants 

 into two classes. Thus the first two plants and their 

 relatives constitute the Class Dicotyledoneae, that is the 

 plants with two cotyledons, while the Water Plantains 

 and their relatives constitute the Class Monocotyledoneae 

 that is the plants with one cotyledon. These classes are 

 of very unequal size, the Dicotyledons containing nearly 

 109,000 species, while the Monocot- 

 yledons contain somewhat less than 

 24,000 species. 



632. It is now thought that the 

 Dicotyledons originated earlier 

 than the Monocotyledons, and that 

 the latter must be considered an 

 ^'''■Fiowe;[;.?p[an^s.*^' early offshoot of the former. Yet 

 the Monocotyledons are by no 

 means higher in rank than the Dicotyledons as a whole; 

 they show fewer variations from a common type; they 

 are more nearly uniform in structure and at no point do 

 they rise as high as do many of the Dicotyledons. For 

 these reasons the Monocotyledons are usually discussed 



