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98 ON THE SEXUAL ORGANS OF THE CYCADACE.5:.
completely analogous to the arcliegonia. The embryo-sac of Gvmno-
sperms holds, therefore, the same position as a spore which remains
contained within the sporangium ; the prothallium, which it produces,
does not make its appearance externally ; the fertilizing matter, in
order to reach the archegonia, has to make its way through the tissues.
The corpuscles, however, indicate by their numerous vesicles, of which
only a single one is fertilized, a much more complicated condition
than exists among the vascular Cryptogams. In these, or at any rate
in the Ferns, there is only a single vesicle, the parent cell of the em-
bryo, or rather of the pro-embryo.
Hofnieister sees, rightly, a great distinction in the fact that in Gym-
nosperms fertilization takes place, as in other Plianerogams, by means
of a pollen-tube, whilst among the vascular Cryptogams this function
is performed by spermatozoids. The contrast is certainly very marked,
anatomically, but it seems less so from a physiological point of view.
The matter which the male element conveys into the female element,
through which it becomes the seat of a new vegetative evolution, is really
of an analogous kind in the two cases. The difference affects more the
external conditions of the function. Among the Phanerogams, an en-
tire cell, the pollen-tube, deprived of its secondary envelope, moves
towards the female cell, to which its fertilizing fluid must be transmitted
by osmotic penetration. Among Cryptogams there are numerous se-
condary cells (spermatozoids) which proceed from the antheridium, and
which— by means of the power of progression possessed by them, and.
under the influence of surrounding conditions—insinuate themselves
into the archegonium, and penetrate into the interior of the female
generative cell. But as to an essential and fundamental opposition be-
tween the contents of the pollen-tube and those of the spermatozoids,
one cannot admit its existence after having learnt, especially from the
researches of Schacht, to ujiderstand the nature of spermatozoids better.*
We must add to this, that amongst the ConifercB, it is not rare to see
the pollen-tube penetrate into the corpuscle after having perforated
its summit.
The parallelism which thus exists between the vascular Cryptogams
* Schacht, 'Die Spcrmatozoiden im rflanzenreicli, 18C4.'— I have no kuowledge
of precise data as to the chemical propertii'S of spermatozoids. It
would not be without interest to ascertain if phospliorus enters into tliem in as
great proiiortiou as into the pollen (compare Corenvvinder in the Ann. des
ycieuccs Is'at. 4nie ser. xiv. p. 49.