CONTORTS. 



548 



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 



Apocynacese 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 waxy, club-shaped pollen- 



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



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



Orchids), must be attached to 



sticky discs (corpuscula) ; 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. 

 The 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 anti- 

 dromous; they are in reality ter- 

 minal, each on its own axis, and the 

 entire floral portion of the shoot is 



FIG. 582. Asclepias cornuti. A An open 

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

 down ; the stamens are bent together and 

 surround the gynceceurn. B The androecium 

 after 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 

 pollinum which is caught by it, is dragged, 

 and behind which the only receptive part 

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

 (r), which secretes the horny corpusculum, 

 which is split at 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 upwsmls, 

 it becomes entrapped in the slit of the cor- 

 pusculum, which is then pulled our, 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 gjnce- 

 ceuin with the pollinia hanging freely, 

 corpusculum and two pollinia. 



E A 



