pdf 25 MB - BSBI Archive

76 ON THE SEXUAL ORGANS OF THE CYCADACEiE.
tissue, a true endosperm. It is now no longer possible to dis-
tinguish the true wall of the embryo-sac ; the space whicli it oc-
cupies is bounded by the dense, smooth, and shining surface of the
dilated nuclear tissue, to which perhaps the debris of the original
amniotic membrane adhere.* It is this which has previously led me
into error, in regarding the embryo-sac as a free cavity in the albumen
which I regarded as deiived from the nucleus, so that I could not
recognize the morphological meaning of the true nucleus, although I
had observed figured and described the different stages of development,
(Ann. des Sc. Nat. 1. c. p. 199 ; Monogr. plate i. iig. r, s.) In nu-
merous unfertilized seeds the endosperm occurred just as in those that
were fertilized ; to my great astonishment, however, I have observed
several isolated cases where it was wanting, though the cavity for its
reception existed.
I know nothing of the changes which take place in the upper part
of the embryo-sac at the first appearance of the second endospermic
formation, nor of the way in which the corpuscles of Brown originate.
I only know the period at which the corpuscles already exist both in
tlie unfertilized ovules and in the ripe seeds containing an embryo. The
vault or upper part of the embryo-sac is very persistent, and becomes
a soft pulpy, often yellowish membrane, to which adheres above, the in-
ternal tissue of the conus nuclei, below, the tops of the corpuscles.
Plate XCI. fig. 12 ^, where the corpuscles do not yet exist; Plate
XCII. fig. 9 a, the remains of the cone with the amniotic membrane ad-
herent, below which are the corpuscles; fig. 10, the part removed with
the corpuscles, which are attaciied to it; fig. 1, the embryo-sac with
the cone removed and viewed from above, with the six areolae or places
where the interior canals of the cone terminate, and to which are
attached on the opposite sides by their opercular rosettes the tops of
the corpuscles ;t fig. 2, tops of the corpuscles situated at this level
fig. 8, corpuscles whose tops exhibit regularly arranged fragments of
tissue! (opercular rosettes (?) or shreds torn from the part where ad-
* Hooker has observed the same thing in ' Welwitscliia,' I. c. p. 32.
f " Juniore a-tate inciiibraua tenuis iiioUissima fere gelatinosa saccos obtegit
et eorum apieibus adha^ret, pimctis obscnris vel areolis paruniper elevatis extua
instrueta,qu£c cum saecorum subjacentium apieibus correspondent," etc. (Ann.
des Sc. Nat. I.e.).
J " Fragmenta regularia, bases probabiliter canaliuni conductorum coni
nuclei exhibentia." Description attached to plates.—W. T. I).
;