272 Scientific Proceedings, Royal Dublin Society. 



mind that the starting-point has been different here from that of a Pteris, 

 to produce Acrostichum aureum. In the latter case the acrostichoid spread 

 was from the margin inwards. But in the case of Platytaenia, if the start 

 were from Taenitis, the spread would be not from a marginal fusion sorus, 

 but from one definitely intra-marginal. The spread might then be either 

 outwards to the margin, or inwards to the' midrib, or both. We know that 

 in Brained, on the disappearance of the indusium, the sorus spreads outwards, 

 which is exactly the opposite of the inward spread to produce Acrostichum 

 aureum. It must remain for developmental examination to show what is 

 actually the case in Platytaenia. But in any case, it is only an analogy which 

 cannot be closely drawn in view of the essential difference of the Pterid from 

 the Blechnoid type. 



The above revision of characters of the genera examined leads to the 

 probability that they are all Blechnoid derivatives with the possible reservation 

 of Paltonium. The nearest genera to the true Blechnoids would be Taenitis 

 and Eschatogramme. The rest have diverged more widely in relation to the 

 epiphytic habit which they show, and consequently their relation to the 

 Blechnoid stock is more or less obscured. There is, however, reason to 

 believe that they are all properly to be regarded as offshoots of the Blechnoid 

 series, characterized by the fusion-sorus of intra-marginal position. 



The work for the above paper was done in Glasgow University during the 

 tenure of a Travelling Studentship from the National University of Ireland. 

 I wish to express my gratitude to Professor Bower of Glasgow University, 

 not alone for having welcomed me to his department, and having given me 

 every facility for the carrying out of the work, but also for his continued 

 interest in its progress, and his kind assistance and direction throughout. 



