150 EMBRYOGENESIS IN PLANTS 



Fig. 33e, f. In short, the embryos of these ferns show growth and 

 structural differences as compared with those of Adian turn or Dryopteris. 

 To what extent some of the growth characters of the Osmimda embryo 

 are related to the presence of an endophytic fungus in the green pro- 

 thallus is a matter of interest, especially in view of the very slow growth 

 and development of the embryo in eusporangiate ferns with holo- 

 saprophytic prothalh. 



In the Gleicheniaceae the embryogeny is also intermediate in 

 character. Precise information is lacking but according to Campbell 

 (1940), who has figured embryos at various stages of development in 

 Gleichenia pectinata and G. linearis, the initial divisions of the zygote, 

 the general segmentation pattern, and the organogeny are as in the 

 Polypodiaceae. The embryo, however, is characterised by a large foot, 

 the axes of the first leaf and root are aligned and their vascular strands 

 continuous, as in the Marattiaceae, and the shoot apex is initially small 

 and inconspicuous but has a definite tetrahedral apical cell. The 

 presence of a vascular strand below the apex has not been definitely 

 ascertained, though its existence seems probable. 



Little is known of the embryogeny in the Schizaeaceae. This is 

 unfortunate, since in species such as Schizaea pusilla the prothallus is 

 typically filamentous and the archegonium almost free, i.e. in contact 

 with the prothallial tissue only at its base. It would be very interesting 

 to know if, in these ferns, the embryogeny follows the same pattern as 

 in Adiantum or OnocJea, where the developing zygote is surrounded by 

 prothallial cells. In Lygodium japonicum Vladesco (1935) found that 

 the sequence of divisions to the octant stage was as usual for lepto- 

 sporangiate ferns. In Aneimia phyUitides, however, after the basal wall 

 has been laid down, the anterior segment is divided by a median wall, 

 whereas the posterior segment is divided by a transverse wall (Vladesco, 

 1935). The further development is, unfortunately, not known but 

 Vladesco states that it does not appear to show any important 

 divergences. 



An incomplete and inexact account of the early development of 

 Hymenophylhim tunbridgense was given by Janczewski and Rostafinski 

 in 1875. Vladesco (1935) states that the arrangement of the primary 

 organs appears to be normal for leptosporangiate ferns, but contrary to 

 the account given by the two authors mentioned above, the first root 

 develops normally, without any precocious disorganisation, and second 

 and third roots are sometimes formed under their corresponding leaves. 

 In many plantlings, however, only one root is formed. Vladesco states 

 that this may be related to the humid environment in which this fern 

 grows. 



In the Hymenophyllaceae, the gametophyte in some species of 



