CONTRIBUTIONS TO BOTANY. 
145 
for the purpose of impregnation, but it afterwards becomes sealed 
up by a distinct deposit and by the adhesion of the base of the 
tubillus to the tercine or integument formed by the contraetion 
or absorption of the body of the nucleus, within which the albu- 
men becomes deposited*. The various changes that take place 
during this action (except the lengthening of the micropyle of 
the secundine) are precisely analogous to those which occur in 
the fecundation and production of seeds in the higher order of 
exogenous plants. 
In Ephedra, if we look upon its style as being entirely reduced 
so that its hollow stigma becomes in consequence depressed 
and fixed in the apex of the ovarium, we have nothing in such 
a case but a modification of the ordinary pistillum ; and under 
this point of view we have no sound reason for giving the name 
of gijmnospermous or naked ovules to the germens of the Gneta- 
ceee. In support of the view thus taken, we find here the female 
organ in its development following the same changes as in some 
of the higher orders of dicotyledonous plants ; for the nucleus 
of a single erect ovule grows into a regular embryo, enclosed in 
albumen, its proper integuments (primine and secundine) finally 
close over the nucleus, and become the testa and tegmen of the 
seed, while the shell of the ovarium, in the usual manner of 
phanerogamous seeds, becomes a coriaceous peihcarp formed of 
ligneous fibres (in Gnetum intermixed with peculiar acicular 
pungent crystals, perhaps analogous to the cystohths of the 
Urticacece) . 
The only circumstance that has favoured the notion of naked 
ovules in the Gnetacece is the absence of a style in the ovary, as 
just mentioned, and the more immediate impregnation of the 
ovule, by the entrance of pollinic boyaux through the aperture 
in its apex, without the intervention of any apparent placentary 
channels. But a very similar mode of impregnation exists in 
numerous other families, where the style is hollow for its whole 
length, leaving a pervious opening into the cell of the ovary : 
this exists in Styracece, Olacacea, and many others. Schleiden 
figures it in Helianthemum f, where several pollinic boyaux are 
seen descending through the styles into the cell of the ovary, 
and fixing themselves upon the micropyle of its several ovules. 
This fact, though not distinctly seen by Brown, was ingeniously 
inferred by him a long while before J. Mirbel shows how this 
is effected in Siatice^, where a cylindrical process (probably 
* Loc. et tab. cit. figs. 21, 24, 26. 
t Nov. Acta Caes.-Leop. xix. p. 56, tab. 8. figs. 131-133. 
J Gen. Remarks, p. 58. 
§ Mem. Acad. Inst. ix. 625, tab. 4. figs. 2, 3, 4. 
VOL. II. 
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