212 



substance in the oblique depression had acquired a nearly membranaceous 

 texture and a light brown colour; and on separating the gland from its fur- 

 row, which was then practicable, this membrane followed it. At this period, 

 too, the contents of each cell of the anthera had acquired a certain degree 

 of soliditv, a deteriuinate form, and were separable from the cell in one mass ; 

 the cuculli were also observable, but still very small apd green, nearly scutelli- 

 form, having a central papilla, the rudiment of the future horn-like process. 

 Immediately previous to the bursting of the cells of the antherse, which takes 

 place a little before the expansion of the corolla, the cuculli are completely 

 formed, and between each, a pair of minute, light green, fleshy teeth are 

 observable, the single teeth of each pair beuig divided from each other by 

 the descending alee of the aniherse. The glands of the stigma have acquired 

 a form between elliptical and rhomboidal, a cartilaginous texture, and a ' 

 brownish black colour; they are easily separable from the secreting furrow, 

 and on their under surface there is no appearance of a suture, or any indica- 

 tion of their having originally consisted of two distinct parts : along with 

 them separate also the descending processes, which are compressed, mem- 

 branous, and light brown ; their extremity, which is still unconnected, being 

 more gelatinous, but not perceptibly thickened. The pollen has acquired 

 the yellow colour, and the degree of consistence which it afterwards retains. 

 On the bursting of the cells, the gelatinous extremity of each descending 

 process becomes firmly united with the upper attenuated end of the corre- 

 sponding mass of pollen. The parts are then in that condition in which they 

 have been commonly examined, and are exhibited in the figures of Jacquin, 

 who, having seen them only in this state, naturally considered these plants as 

 truly gynandrous, regarding the masses of pollen as the anlherse, originating 

 in the glands of the stigma, and mei'ely immersed in the open cells of the 

 genuine antherse, which he calls antheriferous sacs; an opinion in which he 

 has been followed by Roltboell, Koelreuter, Cavanilles, Smith, and Desfon- 

 taines. The conclusion to be drawn from the observations now detailed is 

 sufficiently obvious; but it is necessary to remark, that these observations do 

 not entirely apply to all the plants which I have referred to the Asclepiadese ; 

 some of them, especially Peripioca, having a granular pollen, applied in a 

 very different manner to the glands of the stigma : they all, however, agree 

 in having pollen coalescing into masses, which are fixed or applied to pro- 

 cesses of the stigma, in a determinate manner ; and this is, in fact, the essen- 

 tial character of the order. Dr. Smith, in the second edition of his valuable 

 Introduction to Botany, has noticed my opinion on this subject ; but, probably 

 from an indistinctness in the communication, which took place in conversa- 

 tion, has stated it in a manner somewhat difi'erent from what I intended to 

 convey to him; for, according to his statement, the pollen is projected on 

 the stigma. The term projection, however, seems to imply some degree of 

 impetus, and at the same time presents the idea of something indeterminate 

 respecting the part to which the body so projected may be applied. But 

 nothing can be more constant than the manner in which the pollen is 

 attached to the processes of the stigma in each species." 



This order is one of those which contain indifferently what are called suc- 

 culent plants and such as are in the usual state of other jjlants ; this exces- 

 sive development of the cellular tissue of the stem, and reduction of that of 

 the leaves, is in its greatest degree in Stapelia and Ceropegia ; it is diminished 

 in Dischidia, the succulence of which is confined to the leaves; and it almost 

 disappears in Hoya, the stem of which is in the usual state, but the leaves 

 between fleshy and leathery. 



Geography. Africa must be considered as the great field of Asclepia- 

 dese, especially its southern point, where vaf=.t numbers of the succulent species 



