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ON THE SEXUAL ORGANS OF THE CYCADACE^. 103
pollen can penetrate into the inverted ovule, from their opening, instead
of being directed to the periphery, being applied against the axis of
the cone. The difficulty increases when it happens, as in certain spe-
cies of Dioon and Encephalartos, that the entire cone is covered with
a compact pubescence,—is as if it were enveloped in a tissue of wool.
Nature, however, finds its way, as is proved by the numerous seeds
provided with an embryo which the ripe cone exhibits, as well as in
Conifers, where it is common to see in our climate pollen fixed on the
nucleus. The groups of plants whose origin extends to the palaeozoic
time, show themselves therefore to be independent of insects. They
remain now as at the earliest period of their existence, and we see that
nature adopts other means to bring the microspores into contact with
the macrospores.
Note by the Translator.— In page 74, line 30, the last clause of the
sentence should have been rather more correctly rendered, " It would
be, besides, a structure of which I know no other analogue."
The meaning of the whole passage admits of being made clearer by
a reference to Oudemans' view of the matter which Miquel controverts.
The former writer states that " the epidermis of the entire ovule" (in-
cluding its coat) " penetrates into the micropyliferous tube" (exostome),
" and descends at first vertically, then oblicpiely, to the foot of the
conical protuberance, to the sumnut of which it is reflected so as to
cover it exactly, with the exception of its extremity (' Archives Neer-
landaises,' ii. 1867).
Miquel considers that the epidermis of the coat, and the epithelium
of the nucleus are distinct structures, although intimately united up
to the point, where the cone of the nucleus detaches itself from the
coat.—W. T. D.
EXPLICATIO TABULAEUM.
(Si niliil adnotatum, figui'asnat. magn. deliiieatas intelligas.)
Tab. XCI.
Fig. 1. Pars carpophylli Cycadis revolutce longitudinaliter secta, vasorum fascicules
et canales guramiferos monstrans ; a, pars nuclei libera ; b, cavum
amnii altero stadio incijiiente.
Fig. 2. Ejusdein ovulum, amnii cavitate jam magis aucta.
Fig. 3-4. Eadcm auctiora, nuclei textu ; c, jam partim repulso.
Fig. 5. Idem provectius ; a, integuiuenti stratum exterius molie ; b, stratum