CONTORTS. 



545 



the true stigmas, and the fruit always consists of 2 follicles; seeds 

 most frequently numerous and hairy at the micropyle ("vegetable 

 silk"); endosperm scanty. The order is distinguished from the 

 Apocynaceee and from all other plants also, except the Orchids, by 

 having all the pollen-grains in each of the 2 loculi of the anthers 

 (true 2-locular anthers) united into one ivaxy, club-shaped pollen- 

 mass (" pollinium "), for the purpose of pollination by insects. These 

 heavy masses, in order to secure pollination (as in the case of the 

 Orchids), must be attached to 

 sticky discs (corpuscnla) ; there 

 are 5 corpuscula, one at each 

 of the corners of the 5-angular 

 stylar-head (alternating with 

 the anthers), and to each of 

 these are attached 2 pollinia, 

 one from each of the anthers 

 situated on either side (thus 

 each anther gives its right 

 pollinium to one corpusculum 

 and its left to another). The 

 stamens are frequently united 

 at the base, and each bears on 

 the back a variously formed, 

 petaloid appendage, termed 

 a " cucullus." 



A peculiar relative position 

 (and therefore a good, dis- 

 tinctive characteristic) is often 

 found in the inflorescence, which 

 is cymose ; it is placed between 

 the two leaves of a whorl, 

 nearer to one than to the other. 

 TLe leaf-pairs are placed obliquely 

 in the floral region, at acute and 

 obtuse angles, and not at right 

 angles (as in the purely vegetative 

 parts) ; the inflorescences are placed 

 in two rows only which are nearly 

 90 from each other, and the two 

 contiguous to one another are auti- 

 dromous ; they are in reality ter- 

 minal, each on its own axis, and the 

 entire floral portion of the shoot is 



W. B. 



FIG. 52. Asclepias coniuti. A An open 

 flower with the calyx (7,-)and corolla(c) turned 

 d'>wii ; the stamens are bent together and 

 surround the gynceceuni. -B The aiidrcecinm 

 a r ter removal of the sterile part (cucullus) 

 of the anther, which functions as a nec- 

 tary : e the lateral expansions of the fertile 

 portion of the anthers ; / the slit between 

 the expansions of two contiguous anthers, 

 through which the insect's foot, and later a 

 polliiium which is caught by it, is dragged, 

 and behind which the only receptive part 

 (stigma) is hidden ; above the slit / is the gland 

 (r), which secretes the horny corpusculum, 

 which is split Ht its base and joined on either 

 side with a pollinium (this is more distinctly 

 seen in D and E). When the foot of the insect is 

 caught in the slit (/) and is drawn upwards, 

 it becomes entrapped in the slit of the cor- 

 pusculum, which is then pulled out together 

 with the pollinia firmly attached to it. In 

 walking over the flowers the insect will draw- 

 its foot through other slits (/) and so leave 

 the pollinia on the stigmas. C, D The gynoc- 

 cpum with the pollinia hanging freely. E A 

 corpusculum and two pollinia. 



K N 



