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202 MR. T. H. CORRY ON ASCLEPIAS CORNUTI. 
glycerine and in weak solutions of sugar. Іп both cases the skein of tubes produced 
attained a very eonsiderable length. With strong glycerine the results obtained were not 
so successful, although in many cases rupture occurred slowly, always, however, at the 
same place; but the skeins of tubes which were produced never attained any very great 
length. This seems to have been very much the result obtained by Brown when he 
applied the more convex edge of a pollinium to the superior end of one of the stigmatic 
furrows; for this latter, even in this stage (probably Brown thought to facilitate the 
removal of this body by an insect’s foot) continues to secrete a liquid which moistens 
and lubricates the surface of the cells, though the secretion is now colourless and less 
viscid. He found that rupture of the pollinium and protrusion of the pollen-tubes took 
place more slowly and less completely than when the pollinium was brought in contact 
with the exposed portion of the truly stigmatie surface, as it usually is in pollination. 
Mr. Mansell-Weale* saw a wasp belonging to the genus Pallosoma sucking round the 
corpusculum of ? Xysmalobium lingueforme, Harv., and is disposed to think that 
* this secretion may be of essential service to the flower in attracting the wasps when 
the more abundant store of nectar at the base of the folioles is exhausted." Iam inclined 
to favour this opinion more than that of Brown above quoted, since the corpusculum, 
when mature, lies not at the base, but free at the mouth of its furrow, and is attached to 
the style-table only by its appendages, which are still closely connected with the cells 
which excrete them ; hence it does not require such additional aid to assist in its extrac- 
tion. The principal objection to Mr. Weale's view is that, should it serve the purpose he 
suggests, such a contrivance would be as likely to defeat the object of the mechanical 
apparatus as to favour it, inasmuch as the insect might be satisfied without extracting or 
inserting pollinia; though, on the other hand, having found what it is in search of, it may 
be tempted to remain longer upon the flower, and eventually perform one of the two 
operations whieh together make up the process of pollination. 
With regard to the action of distilled water, I found that rupture of the pollinium 
and protrusion of the tubes did take place in 4. Cornuti, but only after long-continued 
immersion, a result similar to what Brown details in the case of A. phytolaccoides, 
Pursh f. 
The skein of pollen-tubes is found, when its course is traced, penetrating among the 
papillar cells of the tissue forming the real stigmatic surface, in a direct radial line from 
the point where it enters the partially open channel prepared for it, till it arrives at the 
point of union of the style-table with the apices of the two styles. Having arrived at 
this point its course is directed towards the inner side of the apex of that style which is 
nearest to the radius along which it has travelled, and, the papillar tissue of the stigma 
becoming at this point continuous with the tissue lining the interior of the style, the end 
of the skein of tubes passes with ease, in whole or in part, directly into the latter. In 
this it then begins to pursue a downward course towards the ovary. Schleiden {, not- 
withstanding Brongniart's exceedingly accurate account of the inferior stigmatic surface, 
evidently never fully understood the exact method in which the papillar tissue of this 
region was arranged. For although he was aware of the five diverging bands or cords of 
* Loc. cit. p. 53. t Misc. Bot. Works, vol. i. p. 528; Linn. Trans. xvi. p. 728. + Loc. cit. pp. 381, 382. 
