MONOCOTYLEDONS AND DICOTYLEDONS 233 



margin of the leaf, but forms a ' ' closed venation/' so that 

 the leaves usually have an even (entire) margin. There 



are some notable exceptions 

 to this character. 



(4) Cyclic flowers trim- 

 erous. The " three-parted " 



FIG. 215. Two types of leaf venation: the figure to the left is from Solomon's seal, 

 a Monocotyledon, and shows the principal veins parallel, the very minute cross 

 veinlets being invisible to the naked eye; that to the right is from a willow, a 

 Dicotyledon, and shows netted veins, the main central vein (midrib) sending out 

 a series of parallel branches, which are connected with one another by a network 

 of veinlets. After ETTINGSHAUSEN. 



flowers of cyclic Monocotyledons are quite characteristic, 

 but there are some trimerous Dicotyledons. 



Dicotyledons. (1) Embryo with lateral cotyledons and 

 terminal stem-tip. 



(2) Vascular bundles of stem forming a hollow cylinder 

 (Fig. 216, w). This means an annual increase in the diam- 



