September 11, 1914] 



SCIENCE 



367 



surmise, for the conclusions are based on 

 detailed comparison of types occurring in 

 lower horizons with those of the present 

 day. 



I must pass over with merely nominal 

 mention your interesting representation 

 of the ancient families of SchizEeacese, 

 Gleicheniaceffi and Hymenophyllacese, all 

 of which touch the very foundations of 

 any phyletic system of ferns. Also the 

 magnificent array of Dicksonieas and 

 Cyathese, and of the important genus Lind- 

 saya — ferns which take a rather higher 

 position in point of view of descent. But I 

 am bound to devote a few moments to one 

 of your most remarkable ferns, endemic in 

 New Zealand — the monotypic Loxsoma. 



This species has peculiar characters 

 which justify its being regarded systema- 

 tically as the sole representative of a dis- 

 tinct tribe. It is also restricted geograph- 

 ically to the North Island of New Zealand. 

 These facts at once suggest that it is an an- 

 cient survival, a conclusion with which its 

 solenostelic axis, its sorus and sporangium, 

 and its prothallus readily accord. I have 

 lately shown that the Leptosporangiate 

 ferns fall into two distinct series, those in 

 which the origin of the sorus is constantly 

 superficial, and those in which it is as con- 

 stantly marginal. Loxsoma is one of the 

 ' ' Marginales. ' ' It shares this position with 

 the SchizEeacete, Thyrsopteridese, Hymeno- 

 phyllacese and Dieksoniese, and the deriva- 

 tives Davaliese and Oleandrese. Its nearest 

 living relative is probably Thyrsopteris, 

 which is again a monotypic species endemic 

 in the island of Juan Fernandez. There is 

 also a probable relation to the genus Lox- 

 somopsis, represented by one species from 

 Costa Rica, and a second lately discovered 

 in Bolivia. Such a wide and isolated distri- 

 bution of types, which by their characters 

 are certainly archaic, suggests that we see 

 in them the relics of a Filicineous state 



once widely spread, which probably sprang 

 from a Schizseaceous source, and with them 

 represent the forerunners of the whole mar- 

 ginal series. If we look for further en- 

 lightenment from the fossils, it is to the sec- 

 ondary rocks that we should turn. It is 

 then specially interesting that Mr. Ham- 

 shaw Thomas has lately described a new 

 Jurassic fern, Stachypteris Ealli, which has 

 marginal sori, and is probably referable to 

 a position like that of Loxsoma and Thyrso- 

 pteris, between the SchizEeaces and the 

 Dicksonieee. In fact the gaps in the evolu- 

 tionary series of the Marginales are filling 

 up. We may await with confidence fresh 

 evidence from the Jurassic period, upon 

 which Professor Seward is directing an in- 

 tensive interest. 



I should be ungrateful indeed if I did 

 not mention your very full representation 

 of Blechnoid ferns : for developmental ma- 

 terial of several of these has been sent to me 

 by Dr. Cockayne, and others from New 

 Zealand. A wide comparative study of the 

 genus has led me to somewhat unexpected 

 results in regard to the plasticity of the 

 sorus, its phyletic fusions and disruptions. 

 The consequent derivative forms are seen 

 in Woodwardia and Doodya, on the one 

 hand, and on the other in Scolopendrium 

 and Asplenium. These ferns together con- 

 stitute a coherent phylum springing ulti- 

 mately from a Cyatheoid source. The de- 

 tails upon which this conclusion is based I 

 hope to describe in a separate communica- 

 tion to the section. 



And lastly, the Hydropteridese deserve 

 brief mention. Represented in your flora 

 by two species of Azolla, and one each of 

 Marsilea and Pilularia, they typify a condi- 

 tion which must theoretically have existed 

 among ferns in very early times, viz., the 

 heterosporous state. But hitherto, notwith- 

 standing the existence of our living Hydro- 

 pteridese, no fossil fern with microscopic 



