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ON THE SEXUAL ORGANS OF THE CYCADACEii;. 95
common "point of attachment. In tlieir earliest stages they appear as
slightly elevated protuberances or papillae, green in colour, and covered,
by the epidermis, which they do not rtipture. They are, in fact, ex-
crescences of the parenchyma which are formed at particular points^
and their internal tissue is consequently wholly cellular. Little by
little they assume their elongated rounded form, and the entire mass
of cellular tissue becomes pollen-generating tissue, because in the
cavity, when matm'ed, nothing but pollen can be found. Each cell
[' parent cell '] produces four other cells, and each of these forms a
pollen-cell. They are comparable to the regions where, in the loculi
(' loges ') of ordinary anthers, the production of pollen takes place
and should receive, therefore, the name of loculi.
The formation of pollen does not take place over the whole organ as
in angiosperms and most gymnosperms, but only at a considerable
number of points on either side of the median line. The wall of the
loculi is very firm. Its colour is brown at a period a little more ad-
vanced, and its exterior is marked with short linear impressions. It
opens from the top to the bottom on the inner side or that which
is turned towards the other loculi of the group, and sometimes the
slit is prolonged beyond the summit on to the opposite side. Pur-
kinje (' De cellulis antherarum fibrosis ') was not wrong when he
termed the wall " mere epidermidalis," since the loculi are nothing more
than erupted portions of the tissue of the androphyll, covered with the
same epidermis as the rest. I may remark, however, that two cellular
lavers mav be distinauished in this wall which mav be also recoy-nized
in Purkiuje's figures (Plate I. and Plate XVIII., belonging to Zamla
media and Eaccphalartos lotifjifolim). The external layer is the epi-
dermis, the inner one is a parenchymatous layer of peculiar appearance,
composed of porous cells.
The cells of the epidermis have a very narrow lumen. This gives
rise to the superficial stripes mentioned above. The pollen grains ex-
hibit a great uniformity throughout the whole family : they are more or
less elliptical, with a deep longitudinal fold which does not entirely disap-
pear in water. Thus, as Schacht first pointed, out (Pringsheim, Jahrb.
ii. p. 145, plate xvii. fig. 26-28), two secondary cells are also formed
in the intine among the Cycads, so that the structure of the pollen is
comparable in all respects to that of the Coniftrce.
If the views which have just been explained on the subject of the
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