466 



OPHIOGLOSSALES 



never large, but appears only as a slight swelling which remains in close 

 relation with the prothallus. The root rushes forward in its development, and 

 forming its apical cell early (perhaps it is rightly recognised in cell "w" 

 in Fig. 260), it attains a considerable length : it bursts freely through the 

 prothallus before there is yet any definite trace of the apex of the axis 

 or of the cotyledon (Fig. 260 bis). Up to this time the embryo is stored 

 with nutritive substances, but it contains no endophytic fungus. It appears 

 that the development up to this stage occupies several vegetative seasons. 

 The differentiation of the shoot which is thus long delayed accompanies 

 the origin of the second root, which is formed endogenously close to the 

 proximal end of the vascular strand of the first. Immediately above this. 



FIG. 260 



Ophioglossuin vulgatum, L. The central figure shows an archegonium, at period of 

 fertilisation. X225- The left-hand figure shows the first division of the zygote. X225- 

 To the right a more advanced embryo. /, /=basal wall ; ep epibasal ; /y=hypobasal 

 hemisphere ;'/~=the region of the foot ; w = root. X 225. (After Bruchmann.) 



and opposite the neck of the archegonium, the cotyledon and the apex 

 of the axis appear simultaneously, the cotyledon being on the side of th( 

 axis next to the first root : surrounding both axis and cotyledon is the 

 first sheath (Fig. 260 bis, hl^}. The cotyledon remains quite rudimentary : 

 it is followed by a second leaf, which may develop as a small sterile leaf 

 expanded above ground, up to which time the embryo has been growing 

 some eight to ten years. The third leaf, expanded in the following year, 

 may, under favourable circumstances, bear a fertile spike. The further 

 development then follows as in the mature plant. 



Campbell, having examined several tropical species, recognises three 

 types of embryogeny in the genus, that of O. vulgatum, above described : 

 that of O. moluccanuni, described by Mettenius and by himself; and that 

 of O. pendulum^ on which he has added largely to the observations of 

 Lang, and finds that the embryo is variable within the species. According 

 to his statement, the first type is characterised (as we have seen) by an 



