IN ORCniDE.E AND ASCLEPI ADK.E. 525
In tli3 cases now described, the mass, which in p;cneral is entirely concealed by the ahc, was so placed in the lis.sure, that its innei' or more convex edu;e 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 iirndy 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 ])art 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. I'hese 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 ^vere not often to be found even in the tube, especially after it had acquired considerable :725 leno-th.^
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- di-ical, 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 sufHcient length of time in the fissure, — had opened a passage for itself through the membrane, or rather had separated the upper edge of this nieml)rane from
' Tab. 31, li-7.
« Tub. 35, n^s. 7 and 10 ; aud tab. 34, fig. 12.
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