46 WOODY PLANTS OF MASSACHUSETTS. 
jointed leaflets, and are netted and feather-veined, the ribs and 
veins branching and running into each other; while the leaves 
of monocotyledonous plants are without joints, and have parallel 
ribs and veins which do not thus intersect. 
The essential part of the seed of a dicotyledonous plant, the 
embryo, is composed of two cotyledons united by a neck or 
collar to a radicle or future root. ‘The cotyledons are the seed- 
leaves, which, after the germination of the seed in the earth, 
usually expand upon the surface, as is conspicuously the case 
with the beech and the bean. Between these seed-leaves or 
cotyledons rises the plumule, the ascending axis, the future 
stem of the plant. Below them shoots downward the radicle, 
the descending axis or root. 
