200 MR. T. H. CORRY ON ASCLEPIAS CORNUTI. 
towards the open chink, and the whole pollinium has in consequence become somewhat 
larger than it originally was. Brown, who observed them carefully, says that each is 
* about 3455 of an inch in diameter, neither branched nor jointed, and with no apparent 
interruption in its cavity’’*. As the pollen-tubes grow in length they do so apparently at 
the expense of the granules contained in their protoplasm, which are used and converted 
into formative material; for these granules become markedly fewer, and this is more espe- 
cially the case the longer the tube becomes, those in a long tube being few or altogether 
absent. As has been already mentioned, there is no other provision made for the produc- 
tion of these tubes in the form of irregular internal thickenings of the cellulose wall of 
the grain, such as аге to be met with in some plants, e. g., Cucurbita. After extremely 
careful observations many times repeated, I have at length in several cases satisfactorily 
traced the passage for some distance of the larger of the two nuclei which exist in the 
pollen-grain into the pollen-tube, although I have not been able to follow its changes 
further, and I was never able to follow it for any great distance along the tube. The 
larger nucleus, then, does not become broken up and diffused through the protoplasmie 
contents of the grain immediately before the production of the pollen-tube, as Strasburger 
has recently shown that it does in many other Phanerogams, but simply passes in its 
entire concrete form into the proximal end of the pollen-tube. What its subsequent fate 
may be is, however, another matter; but of this I cannot speak definitely ; neither as to 
the fate of the smaller, 2. e. the “ vegetative," nucleus of the pollen-grain can I say much. 
I have never been able to trace its passage into the pollen-tube, although I have carefully 
watched for such an occurrence ; and I have reason to think that it is perhaps redissolved 
immediately before the formation of the pollen-tube, as I was never able to detect its 
presence at that period. 
The granular matter which is sometimes formed, lying between the tubes at their exit, 
Brongniart regards as perhaps due to pollen-grains which have burst without forming 
tubes, and it is exceedingly probable that such is really the case. | 
When the tissue forming the whole inferior surface of the style-table is examined in 
surface view, from the bud stage previous to the expansion of the flower onwards, it becomes 
evident that it is less smooth than is the case with the superior and lateral surfaces of the 
table, which latter are very smooth, possess no papillze, and do not seem to secrete; and, 
further, this inferior surface has a slightly velvety appearance. In longitudinal sections 
it can be seen that this part is formed of cells more elongated and less adherent together 
than those covering the other surfaces. These cells form small papille projecting from 
the inferior surface in a downward and somewhat outward direction. In transverse 
section they are cut slightly obliquely. This papillar tissue makes its appearance at a 
period very soon after the fusion of the two style-apices to form the style-table. These 
papillar cells in the five regions, opposite to the five furrows on the stigmatic angles, 
_ extend almost, if not quite, to the extreme edge of the inferior surface in the form of five 
diverging bands. Тһе five diverging bands are, however, broader than the underlying 
radial grooves. This papillar tissue covers not only the bands but the whole free inferior 
surface of the style-table, the slight pit where the surface bends upwards before meeting 
* Misc. Bot. Works, vol. i р. 595. 
