PHANEROGAMS. 
one. This smaller cell now again undergoes a transverse division parallel to the 
first, and this is sometimes followed by a second ; a two- or three-celled body is 
thus formed, attached on one side to the intine, and projecting into the cavity 
of the larger cell, as in Abietineae, which, moreover, further resembles Ceratozamia 
in the fact that, as in the Coniferae, the large cell, formed by the first division of the 
pollen-grain, developes into the pollen-tube, the mass of small cells remaining 
inactive in the pollen-grain. In Cycas Rumphn, Encephalartos, and Zamia, the 
pollen-grain also splits up, according to De Bary, into a larger and a smaller cell, 
the latter also in this case again dividing once, and the larger cell developing into the 
pollen-tube. The spot where the intine which developes into the pollen-tube breaks 
through the extine lies exactly opposite the mass of small cells (the secondary 
cells of the pollen-grain) ; the extine is in this place thinner, and in the dry 
pollen-grain deeply folded in, so that the transverse section of the dry pollen-grain 
is kidney-shaped. During the absorption of water which 
precedes the formation of the pollen-tube the pollen-grain 
again assumes a spherical form. 
The carpellary leaves are arranged spirally or in apparent 
verticils, closely crowded on the axis of the female flower. 
Those of Cycas have already been described ; in Zamia, 
Encephalartos^ Macrozamia, and Ceratozamia, the carpels are 
much smaller, and each bears only two ovules, attached 
right and left to a peltate expansion which terminates a 
slender pedicel (Fig. 344). The ovule is always orthotro- 
pous, and consists of a large nucellus and a thick integu- 
ment the inner layer of which (in contrast to that of other 
Phanerogams) is penetrated by a number of fibro-vascular 
bundles. The micropyle is a slender tube, formed by the 
prolongation of the contracted margin of the integument 
beyond the summit of the nucellus. According to De Bary's 
researches a second inner integument appears to exist in 
the case of Cycas revoluia. [In the nucellus a group of 
cells can be readily distinguished at an early stage, which 
Warming considers to be homologous with the mother- 
cells of the spores in the sporangia of the Vascular Crypto- 
gams; from one of these the embryo-sac is formed. The wall of the embryo- 
sac becomes thickened, and its cavity becomes filled with endosperm. From 
certain superficial cells of the endosperm the archegonia (corpuscula) are formed. 
The neck of the archegonium consists of two cells. From the large central cell 
a canal-cell is cut ofi", leaving the remainder as the oosphere. After fertilisation, 
each oospore gives rise to a single suspensor ; the embryo is not developed 
at its apex until after the seed has been sown. The embryo of Ceratozamia has 
only one cotyledon ; Cycas and Macrozamia have two ; Van Tieghem has, however, 
found two cotyledons in some cases in Ceratozamia Mexicana, and three in Zamia 
spiralis^ 
In consequence of the form and position of the carpels, the ovules are covered 
and concealed before and after fertilisation, except in Cycas ; at the period of poUi- 
folia (after Juranyi) ; A pollen- 
grain containing a group of three 
(vegetative) cells y; B develop- 
ment of the pollen-tube from the 
large cell of the grain ; e the ex- 
tine, bs the pollen-tube covered 
by the intine. 
