RARY 



TRANSACTION S 



OF THE 



NEW ZEALAND INSTITUTE, 



19 17. 



Art. I. — The Prothallus and Young Plant of Tmesipteris. 



By the Rev. J. E. Hollo way, D.Sc. 



[Received by Editors, 31st December, 1917 ; issued separately, 24th May, 1918.] 



Plates I-III. 



It has been mainly, perhaps, owing to the fact that the various members 

 of the Psilotaceae are confined to tropical and subtropical regions, and to 

 the temperate countries of the Southern Hemisphere, that our knowledge 

 of the gametophyte and of the embryogeny of the sporophyte of this 

 interesting group of plants has increased so slowly. This order has been 

 the last to yield information with regard to the early stages in the life- 

 history of its members, and so to furnish evidence which may help us 

 to form reasonable theories concerning its genetic relationships. The 

 genus Tmesipteris, for example, is confined to Australia, New Zealand, 

 and certain Pacific islands, and hence has remained for the most part 

 beyond the reach of European and American botanists. 



With regard to not a few of the chief pteridophytic groups, not only 

 has the number of those who have searched for the prothallus been 

 limited, but the search itself has been rendered difficult on account of 

 the fact that the gametophyte is often subterranean, and also that 

 although the adult plants are not as a rule rare in their occurrence, yet 

 their abundance in any particular locality is often due largely to their 

 powers of vegetative reproduction, for the germination of the spores 

 seems only to take place in localities where the conditions are peculiarly 

 favourable, and where also the prothallus and young plant will remain 

 quite undisturbed during the protracted period of their development. 

 However, it seems to be evident from the writings of most of those who 

 have given an account of the details of their search for pteridophytic 

 prothalli that when once one can learn from experience in the field to 

 recognize the localities favourable to the development of the particular 

 kind of prothallus searched for there is no obstacle other than the necessity 



1— Trans. 



