SEED-BEARING PLANTS 
455 
stantly associated with the possession of one or two 
cotyledons. Thus, in monocotyledons the leaves are, with 
rare exceptions, parallel-veined, and the growth of the 
stem is endogenous; while in dicotyledons the leaves are 
FIG. 339. Morphology of a typical dicotyledonous plant. A, leaf, 
pinnately-netted veined; B, portion of stem, showing concentric layers of 
wood; C, ground-plan of flower (the parts in s's); D, perspective of flower; 
E, longitudinal section of seed, showing dicotyledonous embryo. 
usually net- veined, and the stem exogenous. In mono- 
cotyledons, also, the parts of the flower usually occur in 
threes (as in Erythronium) , or in sixes, never in fives, while 
