724 Mr. Brown on the Organs and Mode of 



cells. Its membrane is transparent and colourless, made up of 

 two united coats, and the cavity is filled with spherical granules of 

 nearly uniform size, among which a few oily particles are occa- 

 sionally observable*. In this state no appearance or indication of 

 the tubes or appendages described by Dr. Ehrenberg is found. 



On the l6th of July, in repeating my examination of Asclepias 

 purpicrascens'^t I observed in several flowers one or more pollen 

 masses removed from their usual place, namely the cell of the 

 anthera, and no longer fixed by the descending arm to the gland 

 of the stigma, but immersed in one of the fissures formed by the 

 projecting alae of the anthera?, and in most cases separated from 

 the gland, a small portion of the arm or process, generally that 

 only below its flexure, remaining attached to the mass]:. 



In the cases now described, the mass, which in general is 

 entirely concealed bj'^ the alae, was so placed in the fissure, that 

 its inner or more convex edge was in contact with the outer 

 wall of the tube formed by the united filaments, and the gibbous 

 part of the edge closely pressed to that point where this tube is 

 joined to the base of the corresponding angle of the stigma§. 



These masses, at the point of contact, in most cases adhered 

 firmly to the tube or base of the stigma, and on being sepa- 

 rated, a white cord or fasciculus of extremely slender threads or 

 tubes, issuing from the gibbous part of the edge, which had then 

 regularly burst, came into view. 



On laying open the pollen mass, — which in this state was 

 easily done, by first dilating the aperture that gave issue to the 

 cord, — each of the tubes composing it was found to proceed 

 from a grain of pollen. These grains retained nearly their 

 original form, but were become more transparent, and had 

 generally lost a great portion of their granules ; and these 



* Tab. 34. fig. 6 ; and Tab. 56. fig. 3, & 13. f Tab. 34. 



t Tab. 35. fig. 2, 3, 4, & 7. § Tab. 34. fig. 7- 



granules 



