294 PHYLUM 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 
nis 24,000 species. 
532. It is now thought that the 
Dicotyledons originated earlier 
than the Monocotyledons, and that 
the latter must be considered an 
Fre ee eter a2? 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 
MONO. 
atin 
a 
