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1903] , BRIEFER ARTICLES 2S9 



glossum type; in Equisetuin they ar^ regarded as being directly seated 

 . on the axis, and having originated there by a similar progression ; 

 they would thus be non-foliar. It is pointed out that though a foliar 

 theory would be possible for Equisetum itself, it is not applicable to 

 the facts known for the fossil CalamarieaCj which are so naturally related 

 to it. Thus the strobilus of the Equisetineae is of a rather different 

 type from that of the Lycopods, Psilotaceae, or even the Ophioglos- 

 sacae, in all of which there is a constant relation of the spore-producing 

 parts to the leaves; in the Equisetineae no such constant relation 

 exists; the leaves and sporangiophores may be in juxtaposition, as in 

 Calamostachys, without exactly matching numerically; or the sporangio- 

 phores may occur in larger numbers and in several ranks, between sue 

 cessive 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 cer- 

 tain 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 resem- 

 ble the sporangiophores of other Pteridophyta; the more complicated 

 soral conditions of the Gradatae and Mixtae were probably derivative 

 from these, the chief difference being due to the interpolation of new 

 sporangia, an innovation which is in accordance with biological prob- 

 ability, 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 lyco- 

 pods, Psilotaceae, Sphenophylleae, Ophioglossaceae, and Filices illus- 

 trate lines of elaboration of a radial strobiloid type, with increasing 

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

 I characters, into small-leaved Lycopsida, and large-leaved Pteropsida is 



quoted; but it is concluded that the anatomical distinction 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 Ophioglossaceae 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 Ophioglossaceae." The 

 rnore recent investigations of Jeffrey and of Lang have shown, however, 



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