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 Fih'x-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 transverse wait), 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 Pieris aquilina, which 

 the reader may compare with the corresponding development of Salvinia 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 longitudinal section of the embryo oi Pteris aqitiliiia (after Hofmeister, Entwickelung und 



Bau der Vegetationsorgane der Fame, 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, stv being its apical cell and wA 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 epihasal half of the embryo) the two upper (z*. 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 Fame. — Kienitz-Gerloff, Entwickelung des Embryo bei Pieris serrulata, 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 Eqnisetum, Marsilia, Salvinia, and Selaginella, as also of 

 Muscinese: further, Goebel, zur Embryologie der Archegoniaten, Arb. d. bot. Inst, in Wiirzburg, 

 II. 3, 1880.] 



