426 
VASCULAR CRYPTOGAMS. 
that this latter remains for some time enclosed in a protuberance springing from 
the under surface, until the first leaf and root break through. The first processes 
of division of the oospore are, as Hofmeister has shown in the case of Pteris aquilina 
and Aspidium Filix-mas, not entirely alike in different Ferns^. It is certain, how- 
ever, that the first division-wall (called the basal wall) of the oospore is transverse 
to the longitudinal axis of the prothallium, and inclined to it obliquely; as shown 
in Fig. 295, E, its inclination is the same as that of the neck of the archegonium. 
It is also certain that each of the two daughter-cells is at once divided again by a 
wall in the plane of the prothallium (called the Iransverse wall), so that the embryo 
now consists of four cells placed as quadrants of a sphere, and these are further 
divided by a wall parallel to the long axis of the prothallium (called the median wall). 
In Fig. 296 these first transverse divisions are indicated by thicker lines, the embryo 
being seen in longitudinal section. The explanation of the figure points out the 
interpretation which Hofmeister gives to the first four cells of Pleris aquilina, which 
the reader may compare with the corresponding development of Salvifiia and 
Marsilia ; but it must not be forgotten that the embryo of the Fern lies, so to 
speak, on its back. Although it is impossible in this place to go into a more 
Fig. 296.— Vertical long-itudinal section of the embryo of Pteris aqiiilinn (after Hofmeister, Entwickelung und 
Bau der Vegetationsorgane der Farne, p. 607) ; the thicker lines are sections of the first two division-walls by 
which the embryo is divided into four cells (the continuous thick line represents the basal wall). The lower anterior 
cell forms the leaf b; from the upper anterior is derived the stem st ; from the lower posterior cell is produced 
the root, yiv being its apical cell and ivh its root-cap ; the foot y is formed from the upper and posterior of the first 
four cells. 
minute description, it is still necessary at least to point out that a close resem- 
blance exists between the embryo of Ferns and that of Rhizocarps. 
[The embryo now consists of eight cells. Of the four octants which lie in front 
of the basal wall (the epibasal half of the embryo) the two upper {i. e. those nearest 
the neck of the archegonium) give rise the one to the growing point of the stem, the 
other to trichomes, from the two lower octants the first leaf (cotyledon) is developed. 
Of the four octants which lie behind the basal wall (forming the hypobasal half of the 
embryo), the upper two form the foot ; and of the lower two, the one which is diame- 
trically opposite to that which forms the stem gives rise to the root, and the other is 
gradually suppressed.] 
^ [On the embryology of Ferns, see Kny, Keimung und Entwickel. von Ceratopteris, Bot. Zeit. 
1874, and Die Entwickelung der Parkeriaceen, Nov. Act. Acad. Leop. -Carol. 1875. — Vouk, Die 
Entwick. des Embryo bei Asplenium Shepherdi, Sitzber. d. "Wien Akad. 1877. — Leitgeb, ibid. 1878, 
Zur Embryologie der Farne. — Kienitz-Gerloff, Entwickelung des Embryo bei Pteris serriilata, Bot. 
Zeitg. 1878. — A good summary is given by Sadebeck in Schenk's Handbuch, vol. I. Compare also 
the accounts given of the embryology of Eq^dselum, Marsilia, Salvinia, and Selagifiella, as also of 
Muscinese: further, Goebel, zur Embryologie der Archegoniaten, Arb. d. bot. Inst, in Würzburg, 
II. 3, 1880.] : 
