VIII THE PTERIDOPHYTA—OPHIOGLOSSACEyE 239 



off and separate, exactly as in the sporogonium of a Bryophyte, 

 and each cell is, potentially at least, a spore mother cell. 

 Bower ^ states that only a part of the cells produce spores, and 

 that the rest remain sterile and serve with the disorganised 

 tapetal cells to nourish the growing spores. The final division 

 of the spore mother cells into four spores is identical with that 

 of the Bryophytes. 



At maturity the sporangium opens by a cleft, whose position 

 is indicated as we have seen in the younger stages, and as the 

 cells shrink with the drying of the ripe sporangiophore the 

 spores are forced out through this cleft. 



Ophioglossuni vidgatwii and the other terrestrial forms show 

 some points of difference when compared with 0. penduliivi. 

 These grow much more slowly, and longitudinal sections of the 

 upper part of the subterranean stem show several leaves in 

 different stages of development. Each leaf rudiment, as in 

 O. pendulum, is covered by a conical sheath, formed at the base 

 of the next older leaf, and these sheaths are open at the top, so 

 that there is direct communication between the outside air and 

 the youngest of these sheaths which encloses, as in the latter 

 species, the youngest leaf rudiment and stem apex." In these 

 terrestrial forms, also, the sporangiophore is longer stalked, and 

 the lamina of the leaf more clearly separated from the petiole, 

 which is not continued into it. The lamina is relatively broader 

 and the venation more complex, in some species showing also 

 free endings to the ultimate branches. The sporangia, too, 

 project more strongly and are very evident (Fig. 113). Branch- 

 ing of the roots occurs occasionally, and according to Rostowzew ^ 

 may be either spurious or genuine. In the first place an 

 adventive bud, which ordinarily would develop into a stem, 

 develops a single root and then ceases to grow. This root 

 appears to be formed directly from the main root, and as the 

 latter continues to grow the effect is that of a true dichotomy. 

 The latter does occur, but not frequently. 



The formation of adventitious buds upon the roots is the 

 principal method of propagation of some species of OpJiioglossuni, 

 whose prothallia, as we have seen, are apparently very seldom 

 developed. Rostowzew states that these are not developed 

 from the apical cell of the root, but arise from one of the 

 younger segments, and the apical cell is produced from one of 

 ^ Bower (14). - Rostowzew (i), p. 451. ^ Rostowzew, I.e. 



