211 



Anomalies. Pei'iplocu and some others have granular pollen. Corolla 

 valvate in Leptadenia. 



Essential Character Calyx 5-divided, persistent. Coro//a monopetalous, hy- 



pogynous, S-lobed, regular, with imbricated, very seldom valvular, jestivation, deciduous. 

 Stamens 5, inserted into the base of the corolla, alternate with the segments of the limb. 

 Filaments usually connate. Anthers 2-celled, sometimes almost 4-celled in consequence of 

 their dissepiments being nearly complete. Pollen at the period of the dehiscence of the 

 anther cohering in masses, either equal to the number of the cells, or occasionally cohering 

 in pairs and sticking to 5 processes of the stigma either by twos, or fours, or singly. Ovaria 

 2. Styles 2, closely approaching each other, often very short. Stigma common to both 

 styles, dilated, 5-cornered, with corpusculiferous angles. Follicles 2, 1 of which is some- 

 times abortive. Placenta attached to the suture, finally separating. Seeds numerous, 

 imbricated, pendulous, almost always comose at the hilum. Albuinen thin. Embryo straight. 



Cotyledons foliaceous. Radicle superior. Plnmula inconspicuous Shrubs, or occasionally 



herbaceous plants, almost always milky, and often twining. Leaves entire, opposite, some- 

 times alternate or whorled, having ciliae between their petioles in lieu of stipulae. Flowers 

 somewhat umbelled, fascicled, or racemose, proceeding from between the petioles. R. Br. 



Affinities. So closely are these plants allied to Apocynese, that the 

 affinities of the one are precisely the same as those of the other ; I shall 

 therefore, in this place, speak of the difference between those two orders; and 

 of the peculiarities of that more immediately under consideration. Mr. Brown, 

 who distinguishes them, admits {Flinders, 564) that they differ solely in the 

 peculiar character of their sexual apparatus ; but this is of so unusual a kind 

 in Asclepiadeffi, that it justifies a deviation from the general rule, that orders 

 cannot be established upon solitary characters. In Apocynese the stamens 

 are distinct, the pollen powdery (that is to say, in the ordinary state), the 

 stigma capitate and thickened, but not particularly dilated, and all these 

 parts distinct the one from the other. But in Asclepiadese the whole of the 

 sexual apparatus is consolidated into a single body, the centre of which is 

 occupied by a broad disk-like stigma, and the grains of pollen cohere in the 

 shape of waxy bodies attached finally to the -5 corners of this stigma, to 

 which they adhere by the intervention of peculiar glands. For a long time 

 this structure was misunderstood; but Mr. Brown, in a dissertation in the 

 Transactions of the Wernerian Society, placed its true nature beyond doubt. 

 I subjoin the explanation given by this celebrated botanist, whp thus de- 

 scribes the flower of Asclepias syriaca : — 



"The flower-bud of this plant I first examined, while the unexpanded 

 corolla was yet green and considerably shorter than the calyx. At this period 

 the gland-like bodies which afterwards occupy the angles of the stamen were 

 absolutely invisible ; the furrows of its angles were extremely slight, and, like 

 the body of the stigma, green ; the antherse, however, were distinctly formed, 

 easily separable from the stigma, and their cells, which were absolutely shut, 

 were filled with a turbid fluid, the parts of which did not so cohere as to 

 separate in a mass ; of the cucuUi, which in the expanded flower are so 

 remarkable, and constitute the essential character of the genus, there was no 

 appearance. 



" In the next stage submitted to examination, where the corolla nearly 

 equalled the calyx in length, the gland-like bodies of the stigma were become 

 visible, and consisted of 2 nearly filiform, light brown, parallel, contiguous, 

 and membranaceous substances, secreted by the sides of the furrow, which 

 was now somewhat deeper. Instead of the filiform processes, a gelatinous 

 matter occupied an obliquely descending depression proceeding from towards 

 the base of each side of the angular furrow. 



" In a somewhat more advanced stage, the membranes which afterwards 

 become glands of the stigma were found to be linear, closely approximated, 

 and to adhere at their upper extremity. At the same time the gelatinous 



