IN ORCHIDE^ AND ASCLEPIADE^. 525 



111 the cases now described, the mass, which in general 

 is entirely concealed by the alse, 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 separated, 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 transpa- 

 rent, and had generally lost a great portion of their granules ; 

 and these granules were not often to be found even in 

 the tube, especially after it had acquired considerable [735 

 length.^ 



Almost every grain in the mass had produced its tube, 

 and the tubes were directed from all parts of it towards the 

 point of dehiscence. In this state the mass had become 

 more convex from the increased bulk of its contents. 



The tube so produced from each grain of pollen cannot 

 be said to be emitted from it, but is manifestly an elonga- 

 tion of its membrane. These tubes are transparent, cylin- 

 drical, about 1 -2000th of an inch in diameter, neither 

 branched nor jointed, with no apparent interruption in 

 their cavity, and when of great length, which they often 

 attain, are frequently without granular matter. 



I next proceeded to examine the course of the cord, 

 which in most cases, — and indeed in all where the mass 

 had remained a sufficient length of time in the fissure, — 

 had opened a passage for itself through the membrane, or 

 rather had separated the upper edge of this membrane from 



' Tab. 34, fig 7. 



2 Tab. 35, figs. 7 and 10 ; and tab. 84, fig. 12. 



