146 BOTANY. 



CLASSIFICATION OF THE ANGIOSPERMS. 



The angiosperms are divided into two sub-classes : I. Mono- 

 cotyledons and II. Dicotyledons. 



The monocotyledons comprise many familiar plants, both 

 ornamental and useful. They have for the most part elon- 

 gated, smooth-edged leaves with parallel veins, and the parts 

 of the flower are in threes in the majority of them. As their 

 name indicates, there is but one cotyledon or seed leaf, and the 

 leaves from the first are alternate. As a rule the embryo is 

 very small and surrounded by abundant endosperm. 



The most thoroughly typical members of the sub-class are 

 the lilies and their relatives. The one selected for special 

 study here, the yellow adder-tongue, is very common in the 

 spring ; but if not accessible, almost any liliaceous plant will 

 answer. Of garden flowers, the tulip, hyacinth, narcissus, or 

 one of the common lilies may be used ; of wild flowers, the 

 various species of Trillium (Fig. 83, A) are common and easily 

 studied forms, but the leaves are not of the type common to 

 most monocotyledons. 



The yellow adder-tongue (Erythronium americanum) (Fig. 

 81) is one of the commonest and widespread of wild flowers, 

 blossoming in the northern states from about the middle of 

 April till the middle of May. Most of the plants found will 

 not be in flower, and these send up but a single, oblong, pointed 

 leaf. The flowering plant has two similar leaves, one of which 

 is usually larger than the other. They seem to come directly 

 from the ground, but closer examination shows that they are 

 attached to a stem of considerable length entirely buried in 

 the ground. This arises from a small bulb (5) to whose base 

 numerous roots (r) are attached. Rising from between the 

 leaves is a slender, leafless stalk bearing a single, nodding 

 flower at the top. 



The leaves are perfectly smooth, dull purplish red on the 



