REMOVAL OF POLLEN IN ASCLEPIADS. 259 



they can comfortably suck the honey. All parts of the flower are smooth and 

 slippery, and the only way in which an insect can support its weight is by 

 inserting its claws in the slits between the anthers. In endeavouring to take firm 

 hold, the insect draws its claw from one end of the slit to the other, and so becomes 

 attached to the clip-like organ at the back. When the insect's foot is withdrawn 

 the two pollinia adherent to the clip are dragged out of their niches. One of the 

 claws on that foot is then seen to be wedged between the arms of the clip, whilst 

 the two pollinia are suspended from it (see iig. 269 ^). 



The subsequent history of the pollinia does not strictly belong to the subject of 

 this chapter, but it will be convenient to follow them to their destination. The 

 pollen-masses must be conveyed to stigmas of other flowers. The question is, 

 where are these stigmas to be found? The pentagonal central column, surrounded 

 by the five anthers, contains the ovary in its interior. The approaches to this 

 organ lie through the so-called stigmatic chambers, which are situated close beneath 

 the truncate end of the column, and open outwards. The chambers are concealed 

 in the slits, just as were the clip-like organs, and insects occasionally come across 

 them as they move theii^ claws about in the recesses. If the foot inserted by an 

 insect has pollinia already attached to it, they are thus introduced into the slit in 

 a new flower, and as the insect feels about for firm support it thrusts the pollinia 

 into the stigmatic chamber. When the foot is subsequently withdrawn, the 

 ligatures attaching the pollinia to the little clip are broken, and the pollinia are 

 left in the chamber, whilst the actual clip maintains its grip of the claw. A second 

 organ of the kind with its pollinia may become attached to the insect's foot on this 

 occasion, and the process may indeed be repeated a number of times. Insects 

 caught after visiting flowers of Asclepias Cornuti have often been found to have 

 from flve to eight of these clips fastened to a single foot. 



Other members of the Asclepiadaceje have essentially the same mechanism, 

 though differences in detail of course occur. Very interesting is the result of 

 cultivating the asclepiad Araujia albens (Physianthus albens of gardeners) in 

 regions in which it is not indigenous. This plant is a climber from S. Brazil and 

 Buenos Ayres, and being an ornamental plant is cultivated in gardens in various 

 parts of the world. In its own country it is visited normally by humble-bees, and 

 the curious phenomenon to be described has not been reported as occurring there. 

 But in other localities its sweet-smelling, tubular flowers are visited by hosts of 

 moths, which are apparently unacquainted with the mechanism of the pollen- 

 masses, &c., and get trapped by their probosces in the slit-like notches, which are 

 present between the anther-wings. These wings are rigid, and the slit narrows 

 upwards, and moths visiting the flowers for honey get their probosces jammed in 

 the slits. The result of their struggles to free themselves is only to fix their 

 probosces the tighter in the narrow end of the slit, and the moths die a lingering 

 death with their heads concealed in the tubes of the corollas, and their abdomens 

 projecting. Reliable testimony of this moth-catching propensity of Araujia albens 

 is forthcoming from Massachusetts (Providence), from Italy (Cagliari), and from 



