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 Isoeles, 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 surfa-ce ; 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 Isoeles. 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 Development of the Embryo. 

 The first division of the oospore (formation of the basal wall) differs 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 Isoeles 

 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.] 



