12 Mr. Don's Obser'vatlons on the 



been noticed in the figures and descriptions of the plant which have recently 

 appeared in the Botanical Magazine and Register. I am inclined to think 

 that Tropa'olum dipetalum of the Flora Peruviana will prove to be a second 

 ■species of this genus, and it is possible that Tropceolum may include the types 

 of other genera, when the nature of the fruit in the different species becomes 

 better known. 



Tlie genus Tropceolum was originally included by Jussieu among his Gerania; 

 but he afterwards changed his opinion somewhat, in considering it the type of 

 a distinct group ; still adhering, however, to his former views of its affinity, 

 by continuing to place it next that family, in which he has been followed by 

 Richard, DeCandolle, Auguste de Saint-Hilaire, and other botanists of deserved 

 eminence. The Tropceolece differ in many important points of structure from 

 the Geraniacece, particularly in the want of symmetry between the stamina 

 and other parts of the flower ; in the structure of their stigmata ; in their 

 thick, fleshy cotyledons, with the short radicle placed between their lobes; in 

 the conspicuous plumule, by their axillary flowers ; and finally in the absence 

 of stipules. They have always appeared to me to be more nearly related to 

 the CapparidecE than to any other family, being principally distinguished from 

 them by the quinary arrangement of the petals and lobes of the calyx. In the 

 hypogynous insertion and indefinite number of the stamina, in the inequality 

 of the petals, pendulous ovula, thick, fleshy cotyledons, absence of albumen 

 and stipules, and in tlie axillary inflorescence, both families agree precisely. 

 In the Tropceolece there is likewise an evident indication of the pistilliferous 

 column so conspicuous in Cappariclece. On comparing this family with the 

 Hippocastcmece many striking analogies present themselves ; such, for example, 

 as the quinary arrangement of the petals and lobes of the calyx, the absence 

 of symmetry between the stamina and other parts of the flower, in the struc- 

 ture of the ovarium, which in both is formed by the union of three, mostly 

 nionospermous carpels, in the absence of albumen, in the structure cf the 

 embryo, having large, thick cotyledons, which become united as the seed 

 advances towards maturity, with a conspicuous plumule, and a disproportion- 

 ately small radicle. It is interesting to trace these remarkable coincidences 

 in structure between families, which apparently have no real affinity together : 

 for, although the Hippocastanece are chiefly distinguished from Tropxolece by 



