Holger Jørgensen: The Pollination of Asclepias cornuti Dcne. 3 



As there does not exist any investigation of the pollination of 

 Asclepias cornuti as yet, founded as far as possible upon direct ob- 

 servations, it may be to the purpose to bring one forward in order 

 quite to elucidate the question. 



First we must emphasize the difficulty of a direct perception 

 of the details during the pollination, the pollinating insects moving 

 very quickly and restlessly from flower to flower ; but so much the 

 more carefully one ought to observe the facts of the pollination that 

 really are to be seen, and the features of the structure of flower and 

 insect which are of importance at the pollination. 



From a minute examination of the insects, humble-bees, which 

 in the botanical garden of Copenhagen pollinate A. cornuti, it appears 

 that the corpusculum may be fixed in two places, viz. upon the pro- 

 boscis, where the corpusculum encloses the utmost joint of the palp 

 of the lower-lip (Palpus labialis), and upon the foot, where the 

 corpusculum is fixed upon the pulvillus, the small plate between 

 the two claws of the foot. The proboscis is of no importance to the 

 pollination. Hildebrandt and Müller do not mention any corpus- 

 cula at all upon the proboscis, and in the bot. garden of Copenhagen 

 corpuscula may, as mentioned above, be found upon probosces of 

 insects ; but in the first place it is much more seldom to find corpus- 

 cula upon the proboscis than upon the foot, secondly the pollen- 

 masses have seldom been removed from corpuscula fixed upon the 

 proboscis. As to the position of the corpusculum upon the foot, 

 opinions have been divided. H. Müller for instance believed the 

 corpuscula to be fixed upon the claws, whereas N. E. Brown in a 

 foot-note to Corry's text states that the claws are of very little 

 importance at the extraction of the corpusculum, and Robertsox 

 holds that the corpusculum may be fixed upon the claws, upon the 

 pulvillus, and upon the stiff hairs of the foot. The most recent invesl - 

 igator, Zander, has always found the corpusculum fixed upon the 

 pulvillus, and this agrees with my own observations. On an examina- 

 tion of the literature, one might hesitate to take Zander's statement 

 of the position of the corpusculum to be of universal validity; but 

 for one thing the literature proves that it is not easy summarily to 

 observe where upon the foot of the insect the corpusculum is placed, 

 for we may not, I suppose, take it that Müller really always found 

 the corpuscula fixed upon the claws, when Zander, who, even as 

 Müller did, studied the pollination in Germany, always, and 



