﻿i 9 16] BRIEFER ARTICLES 73 



In order that an insect may effect pollination it is necessary for it 

 to wedge its foot in the slit of the column when climbing about over the 

 flower or scrambling to reach the nectar in the hoods. This is usually 

 not a difficult thing to do, and when once it is caught a sharp pull 

 is necessary to extricate the foot. When the insect is free we find, 

 if we examine its leg, a corpusculum firmly fastened to it by means of 

 the cliplike arrangement, and to the corpusculum we find the pollinia 

 attached. If the insect now goes on with its work of gathering nectar, 

 it is usually not long until it is again caught in the slit. This time 

 it draws into it the pollinia previously obtained and with another 

 vigorous pull it breaks the bands connecting the pollinia with the 

 corpusculum and escapes. The pollinia left in the slit are now in 

 contact with the stigmatic surface. By these processes pollination is 

 effected. 



The jewel milkweed differs from the typical asclepiad in several 

 important respects. The flowers are nodding instead of erect, and, as 

 a direct adaptation to this, the hoods are closed except for a small 

 opening at the apex; the horn is small and included or hidden within 

 the hood; the lips of the slit are firmly closed, and instead of offering 

 an easy entrance to their trap seem to make the entrance difficult. 

 In many kinds of milkweed the hoods and the upper part of the column 

 are borne on a pedicel several millimeters in length. The hoods are 

 sessile in Asclepias cryptoceras. 



The pollination of the jewel milkweed, in southwestern Colorado at 

 least, is apparently accomplished by only one species of insect, a huge 

 bumblebee (Bombus Morrisoni Cressn.). 1 This huge bee is a full match 

 for the large flower, yet it has a rather difficult time obtaining the nectar. 

 Since the flowers are nodding and since the pedicel is absent, there are 

 no footholds offered, and the bumblebee must continually scramble to 

 keep its position. The hoods guide its feet to the slits, and the bee 

 forces them open, and in order to free itself loosens the corpusculum and 

 drags out the pollinia firmly fastened to its feet. When they dry they 

 are in a convenient position to enter the next slit that chances to open 

 in the bee's scrambling for a foothold. 



The fragrance of the flowers is so intense that one would imagine 

 many insects would be attracted, yet such is not the case. In my 

 observation of this plant during the spring of 1914 in southwestern 



1 My thanks are due Professor Cockerell of the University of Colorado for the 



