204 VEGETABLE ORGANOGRAPHY. 



plant ; there are seeds where it is presented under the 

 appearance of a little sharp point, hardly visible ; there 

 are others where it already has small leaves visible, to 

 which the name of Primordial Leaves is given. In 

 general, the gemmule, on developing at the period of 

 germination, presents all the appearances of a young 

 branch which proceeds from a bud furnished with leaves. 

 In some cases, such as Cactus Melocactus, Euphorbia 

 Canariensis, and in general, in succulent plants with 

 very small leaves, it is very thick, fleshy, round, and 

 devoid of leaves : in this case it has sometimes been 

 taken for a single cotyledon ; but on observing it more 

 closely, we find the two cotyledons very small it is true, 

 and, as it were, concealed in the mass of the gemmule. 

 Embryos, with this kind of gemmule, have received the 

 name of Macrocephalous ones. 



The name of Cotyledons, as we have said above, is 

 given to the first leaves of the plant already formed, and 

 visible in the seed. That they are leaves is easily proved : 



1st. By their usual transformation into leaves, and 

 becoming green at germination. 



2d. By their respective position, similar, or analogous 

 to that of the plant already developed. 



3d. By their structure, exactly resembling that of 

 leaves ; and because they are generally furnished with 

 vessels, and stomata distributed in the same manner. 



4th. Because, in plants where the leaves present 

 peculiar phenomena, such as the mobility of those of 

 the Sensitive-plant, or the presence of glands in those 

 of Hypericum, or Gossypium, (PI. 23, fig. 1), &c, 

 the cotyledons present the same characters. 



5th. Because their development, death, and fall, are 

 analogous to what takes place in ordinary leaves. 



6th. Because the cotyledons are absent in plants 

 devoid of leaves, as Cuscuta. 



