MONOCOTYLEDONS AND DICOTYLEDONS 377 
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. 333. 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. 334, w). This means an annual increase in the diam- 
