60 ELEMENTS OF STRUCTURAL BOTANY. 



are attached, and from which the root is developed, is 

 called the radicle, a term meaning " little root." As it is 

 strictly, however, a rudimentary stem, and not a root, the 

 term caulicle would be better. Between the cotyledons, 

 at the summit of the radicle, you will find a minute upward 

 projection. This is a bud, which is known as the plumule. 

 It developes into the stem. 



80. If you treat a Pea or a Bean (Figs. 80, 81) in the 

 same manner as the Cucumber seed, you will find it to be 

 Fig. so. constructed on the same plan. The em- 



bryo of the Bean is dicotyledonous also. 

 But you will observe that in these cases 

 the embryo occupies the whole of the in- 

 terior of the seed. In describing the seed 

 of the Buttercup, it was pointed out that 

 the embryo occupies but a very small 

 Fig. siT" space in the seed, the bulk of the latter 

 consisting of albumen. Seeds like those of the Buttercup 

 are therefore called albuminous seeds, while those of the 

 Bean and Pea are exalbuminous. But, notwithstanding 

 this difference in the structure of the seed, the embryo of 

 the Buttercup, when examined under a strong magnifier, 

 is found to be dicotyledonous like the others. In short, 

 the dicotyledonous embryo is a character common to all 

 the plants we have examined common, as a rule, to 

 all plants possessing the other characters enumerated 

 above. From the general constancy of all these charac- 

 ters, plants possessing them are grouped together in a vast 

 Class, called Dicotyledonous plants, or, shortly, Dicoty- 



ledons. 



Figa 80 and 81. -Seed of the Bean. 



