472 
VASCULAR CRYPTOGAMS. 
of an accumulation of protoplasm. This tissue afterwards produces the archegonia, 
and is therefore the true prothallium ; but a few weeks after the dissemination free 
cell-formation begins beneath it in the spore-cavity, finally filling up the whole cavity, 
and forming a large-celled tissue, which Pfeffer, supported by considerations with 
which I also agree, compares to the endosperm of Angiosperms, and, following 
this analogy, calls by the same name. At the period of fertilisation and of the 
formation of the embryo, the macrospores of Selaginella contain, therefore, both 
a prothallium and an endosperm. The formation of the archegonia begins even 
before the rupture of the exospore, which occurs in this genus in the same manner 
as in Isoeies. The first archegonium originates at the apex of the prothallium ; the 
others arise, whether the first is fertilised or not, in centrifugal succession on the 
exposed parts of the prothallium. 
In both genera the archegonium originates by division of a superficial cell 
parallel to the surface ; the upper of the two new cells divides into four cells placed 
crosswise, each of which splits by an oblique division into two, one lying over the 
other; in this way the neck is formed, consisting of four rows, each of two cells 
in Selaginella, and of four cells in Isoeies. The lower of the first two cells sends 
out a narrow prolongation between the neck-cells, which becomes the canal-cell 
of the neck (Fig. 331 II). The lower larger portion, the central-cell according 
to Janczewski, then has a small portion of its protoplasm cut off which corresponds 
to the ventral canal- cell of the other Archegoniata, the remainder constituting the 
oosphere. The two canal-cells become mucilaginous and are extended from the 
opened neck so as to permit the access of the antherozoids to the oosphere. 
2. The Asexual Generation (Sporophore). The Developmenl of ike Embryo. 
The first division of the oospore (formation of the basal wall) diff'ers from that of 
Ferns and Rhizocarps, taking place perpendicularly to the axis of the archegonium. 
According to Hofmeister, each of the two cells first formed is divided in Isoeies 
in a plane at right angles to that of the first division, the relation of which to 
the first root, the first leaf, the stem, and the foot of the embryo, requires yet 
further elucidation \ The formation of the embryo of Selaginella has recently 
been investigated in detail by Pfeffer. From an elongation of the upper half 
(hypobasal) of the oospore is formed the Suspensor, a body which is wanting in all 
other Cryptogams, but universally present in Phanerogams, and through which Sela- 
ginella consequently approaches flowering plants. The suspensor seldom remains 
^ [According to Bruchmann (Jenaische Zeitschrift, 1874) the upper (epibasal) cell grows 
rapidly towards the neck of the archegonium and produces the apex of the stem and the first leaf 
(cotyledon) ; at the lower part of the anterior surface of the cotyledon a cell grows out and gives rise 
to the ' ligula,' and it is the cells lying immediately at the base of this organ which constitute the 
growing point of the stem. The lower (hypobasal) of the two primary cells grows slowly downwards 
into the spore, forming the foot ; from the superficial cells of that part which is diametrically 
opposite to the growing point of the stem the primary root is developed. From the more recent 
researches of Kienitz-Gerloff (Bot. Zeitg. 1881) it appears that the first divisions of the oospore 
resemble those in the Filicinese (see supra, p. 426). The two anterior superior (epibasal) octants 
give rise to the cotyledon, the two posterior (hypobasal) superior octants to the root, and the four 
inferior to the foot. The ligula is developed from one of the cotyledonary octants ; from the root- 
octants a cotyledonary sheath is also developed. He does not agree with Bruchmann that the root 
has an exogenous origin.] 
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