184 



this is by no nieans necessarily the case. However, it seems 

 highly probable that the extraordinary development of the 

 roots in 0. pendulwn and 0. vulgatum and the protracted sub- 

 terranean life in these species, is a secondary phenomenon asso- 

 ciated with the pronounced saprophytic life of the gametophyte. 



Admitting that 0. moluccanum represents the most primitive 

 type of the group, we should assume that from this was 

 developed in one direction the type of 0. pendulum, in which 

 the development of roots and the long subterranean life are 

 intensified by its marked saprophytic habit, but in which the 

 final development of the definitive sporophyte is essentially the 

 same as in (). moluccanum. 



In another direction the formation of the stem apex is 

 referable to the embryo itself, and the definitive sporophyte is 

 the direct prodnct of the embryo. This condition becomes more 

 strongly marked in Botrychium and Helrainthostachys, between 

 which and 0. moluccanum, 0, vulgatwn may be said to form 

 an intermediate stage. 



Among the other Pteridophytes there are two groups which 

 show some points of resemblance to the type of embryo found 

 in Ophioglossum. In both Equisetum and the Marat tiaceae 

 there is the same bipolar arrangement of the primary organs. 

 In the Marattiaceae the cotyledon grows upward through the 

 prothallial tissues and the root downward, the young embryo 

 in section presenting an appearance not very different from 

 that found in 0. moluccanum except that the stem apex is 

 present. The same is true of Botri/cliium ohliquum. 



The resemblance in Equisetum is not so obvious as naturally 

 the relation, if it exists, is far more remote. However, it is 

 conceivable that from the same original type as that from 

 which Ophioglossum came, there may have developed one in 

 which the epibasal region formed a conical body with its apical 

 cell, and developed into a single spore-bearing structure — 

 the leaf as we have it in Ophioglossum. In another direction 

 the same rudiment formed a stem apex, such as occurs 

 in Equisetum. It is interesting to note that in Equisetum, 



