624 ON THE EMBRYO OF TROPGOLUM MAJUS. 
Schleiden’s Memoir, given in Annales des Sciences Naturelles, 
Tom. ii., particularly to p. 140, and the figures illustrative of 
Tropeolum majus; as it is only through that medium that I 
know anything of Schleiden's previous labours. 
Both Schleiden and Giraud assert that there is a visible 
conducting channel of tissue from the style, through the 
carpellary cavity, as far as the exostome. After very careful 
scrutiny, I find not the smallest evidence to support this 
statement. To prove these observers absolutely in the 
wrong, is, of course, impossible; but in the same mode that I 
impeach Schleiden's testimony, I may argue against that of 
Giraud. He states that the nucleus is covered by only one 
integument; but the ovule unquestionably consists of two, 
viz., the primine and secundine, the latter of which projects 
beyond the primine to form the micropyle, and although 
these coats are blended below, they are decidedly separate at 
the top of the ovule. It is more difficult to discern the exact 
limit between the secundine and thenucleus. The existence 
of the latter is most apparent in the lower part of the ovule, 
where it forms a yellowish flask-shaped body, more opaque 
than the surrounding mass. Schleiden’s fig. 40 does not 
faithfully represent it. The internal cavity is nearly as it is 
exhibited in that figure; but its apex reaches higher up, 
almost to the micropyle, and it is lined throughout with a — 
very delicate lax membrane, which is the Embryo-sac. It is 
that which encloses, and immediately surrounds the oblong . 
body from which is produced the nascent embryo, at the period 
when it first becomes intelligible, namely, some days after 
fecundation, and only a short time before the faded corolla 
falls away, a period not well marked in Giraud’s paper. I - 
cannot find any proof, in all my numerous investigations, of — 
the introversion of the sac embryonnaire, in the manner 
assumed by Schleiden ; and in this plant his hypothesis is 
quite contradicted by the fact that when the embryo has 
descended half way down the cavity, the pedicel which sup- 
ports it is still surrounded by the lax membrane: this fea- 
ture may easily escape the notice of an incautious or unskilful 
