SEED-BEARING PLANTS 



455 



which are quite constantly 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 







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. 



leaves are usually net- veined, and the stem exogenous. In 

 monocotyledons, also, the parts of the flower usually occur 

 in threes (as in Erythronum) , or in sixes, never in fives, while 



