STRUCTURE OF SEED. 205 



7th. Because, when they are opposite they bear in 

 their axils as opposite leaves, sometimes a single ter- 

 minal gemmule, at other times, three small ones ; a 

 central one, which is the prolongation of the cauliculus, 

 and two axillary ones. 



8 th. Finally, because the analogy of the radicle to 

 the root, and of the plumule to the stem, having been 

 proved, that of the cotyledon to the leaves, is an evident 

 consequence. 



The principal difference that plants present, as to 

 their cotyledons, results from the respective position of 

 those organs which are distributed in two manners : 

 the first takes place when two or more are situated 

 upon the same horizontal plane, and then they are 

 opposite or verticillate ; as the first case is by far the 

 most frequent, we give to the whole class of plants, 

 with two or more cotyledons, the name of Dicotyle- 

 dons. When it is necessary to express positively, that 

 the cotyledons are verticillate, we call the plants Poly- 

 cotyledons, but they cannot be considered as a class. 

 In fact, 1st very similar plants present both these 

 manners ; thus, Pinus (PI. 23, fig. 2) and Abies among 

 the Coniferae are polycotyledonous, and the other genera 

 of the family dicotyledonous ; 2d. also in polycotyledo- 

 nous genera or species, the number of cotyledons is not 

 regular ; 3d. in several, they are disposed in two opposite 

 parcels, which seem to refer to the primitive type of the 

 class ; 4th. in all verticillate cotyledons, as in all, or 

 nearly all verticillate leaves, we only find two opposite 

 buds, besides the central prolongation of the stem ; 

 5th, some species with two cotyledons accidentally pre- 

 sent three or four, as I have seen in the French bean, 

 Ranunculus, and Cabbage ; 6th, lastly, I have above 

 said (Book II. chap. iii. sect. 7,) that the distinction be- 

 tween opposite and verticillate leaves is very uncertain ; 



