414 Mr. Robert Brown on the Structure of the 
changes consequent to real, or even to spurious fecundation, 
must take place within the nucleus: and that the albumen, 
properly so called, may be formed either by a deposition or 
secretion of granular matter in the utriculi of the amnios, or 
in those of the nucleus itself; or lastly, that two substances 
having these distinct origins, and very different textures, may 
co-exist in the ripe seed, as is probably the case in Scitaminez. 
On the subject of the ovulum, as contained in an ovarium, 
I shall at present make but one other remark, which forms a 
necessary introduction to the observations that follow. 
On the Structure of the female Flower in CycADEE and 
ConIFER&. 
That the apex of the nucleus is the point of the ovulum 
where impregnation takes place, is at least highly probable, 
both from the constancy in the appearance of the embryo at 
that point, and from the very general inversion of the nucleus ; 
for by this inversion its apex is brought nearly, or absolutely, 
into contact with that part of the parietes of the ovarium, by 
which the influence of the pollen may be supposed to be com- 
municated. In several of those families of plants, however, 
in which the nucleus is not inverted, and the placentze are po- 
lyspermous, as Cistineze *, it is difficult to comprehend in what 
manner this influence can reach its apex externally, except on 
the supposition, not hastily to be admitted, of an impregnating 
aura filling the cavity of the ovarium ; or by the complete se- 
paration of the fecundating tubes from the placentae, which, 
however, in such cases I have never been able to detect. 
It would entirely remove the doubts that may exist respect- 
ing the point of impregnation, if cases could be produced 
where the ovarium was either altogether wanting, or so imper- 
fectly formed, that the ovulum itself became directly exposed 
to the action of the pollen, or its fovilla; its apex, as well as 
the orifice of its immediate covering, being modified and de- 
veloped to adapt them to this economy. 
But such, I believe, is the real explanation of the structure 
of Cycadez, of Coniferze, of Ephedra, and even of Gnetum, 
of which Thoa of Aublet is a species. 
To this view the most formidable objection would be re- 
moved, were it admitted, in conformity with the preceding ob- 
* This structure of ovulum, indicated by that of the seed, as characte- 
rizing and defining the limits of Cistinea, (namely, Cistus, Helianthemum, 
Hudsonia and Lechea,) I communicated to Dr. Hooker, by whom it is no- 
ticed in his Flora Scotica, (p. 284,) published in 1821 ; where, however, an 
observation is added respecting Gzertner’s description of Cistus and Helian- 
themum, for which I am not accountable. 
servations, 
