262 



Prof. F. 0. Bower. Studies in the 



[Jan. 30, 



OphioglossaceaB, in all of which there is a constant relation of the 

 spore-producing parts to the leaves ; in the Equisetinese no such con- 

 stant relation exists ; the leaves and sporangiophores may be in juxta- 

 position, as in Calamostachys, without exactly matching numerically ; 

 or the sporangiophores may occur in larger numbers and in several 

 ranks, between successive leaf-sheaths, as in Phyllotheca and Bornia; 

 or without any leaves at all, as in Equisetum, Thus, on a non- 

 phyllome theory the latter may be held to be only an extreme case of 

 what is seen in certain fossils. 



The Ferns, notwithstanding their apparent divergence of character 

 from other Pteridophytes, may also be regarded as strobiloid forms, 

 with greatly enlarged leaves; the primitive sori of the Simplices 

 resemble the sporangiophores of other Pteridophytes ; the more com- 

 plicated soral conditions of the Gradatae and Mixtse were probably 

 derivative from these, the chief difference being due to the interpolation 

 of new sporangia, an innovation which is in accordance with biological 

 probability, as well as with the palaeontological record. 



The effect of the results thus obtained on the systematic grouping 

 of the Pteridophytes is then discussed; it is pointed out that the 

 Lycopods, Psilotaceae, Sphenophyllea?, Ophiogiossacese, and Filices 

 illustrate lines of elaboration of a radial strobiloid type, with increas- 

 ing size of the leaf. The division of Pteridophyta by Jeffrey, on 

 anatomical characters, into small-leaved Lycopsida, and large-leaved 

 Pteropsida is quoted ; but it is concluded that the anatomical distinc- 

 tion of Jeffrey does not define phylogenetically distinct races, but is 

 rather a register of such leaf-development as differentiated them from 

 some common source. It is contended that the Ophioglossacese and 

 Filices, which constitute Jeffrey's Pteropsida, are not necessarily akin 

 on the ground of their large leaves, and consequent phyllosiphonic 

 structure ; but that they probably acquired the megaphyllous character 

 along distinct lines. The opinion of Celakovsky is still held, " that 

 the Lycopods are probably of living plants, the nearest prototypes of 

 the Ophioglossacese." The more recent investigations of Jeffrey, and 

 of Lang, have shown, however, that in the gametophyte of the Ophio- 

 glossacea?, there is an assemblage of " Filicinean " characters, which 

 differ from those of Lycopodium itself. But Celakovsky's comparison 

 is tvith the Lycopods, not with the genus Lycopodium ; so far as the facts 

 go, increasing " Filicinean " characters of the gametophyte follow in 

 rough proportion to the larger size of the leaf ; thus from Isoetes we 

 learn that a combination of cross characters is found in a mega- 

 phyllous Lycopod type. What we find in the Ophioglossacere is that 

 in conjunction with their more pronounced megaphyllous form, still 

 retaining, however, the Lycopodinous type of the sporophyte, they 

 show more pronounced "Filicinean" characters of the gametophyte, 

 and of the sexual organs. Tt is unfortunate that the facts relating to 



