XXXII] LOPHOSORIA 287 



sorus and sporangium is very similar to that of Gleiciienia: but here only 

 16 spore-mother-cells are formed, and the tale of spores is typically 64: 

 a much smaller number than in any Gleichenia. Nevertheless in Platyzoma 

 still smaller numbers have been found pointing to a typical number of 32, 

 or sometimes of only 16 spores in each sporangium. Thus in development 

 and in soral relation the sporangia of Lophosoria resemble those of 



b 



Fi" -.\. Sporaneia ol Lophosoria, from three different aspects, a, presenting the distal or peripheral 

 facV. b, presenting the proximal or basal face, c, seen from the side, and showing the irregular 

 stomium, with partial duplication. ( x lOO.) 



Gleichenia, but they differ in their lateral dehiscence, while in their spore- 

 output they point rather to the Cyatheaceae. 



The spores are large and tetrahedral, and on germination they produce 

 a prothallus at first filamentous, which widens into a spathulate form with 

 unequal lobes, as is seen in Alsophila. The antheridia are of the usual type, 

 and open by the extrusion of a single cell. 



Comparison 



It must be understood that in this whole discussion the Dicksonieae are 

 excluded, their probable relation being with the Marginal Schizaeaceae. 

 Wherever the Cyatheaceae are named, the word is used in the restricted 

 sense, i.e. exclusive of the Dicksonieae. 



It is seen from the above description that Lophosoria.— \\\nc\\ .systematists 

 have usually ranked with gradate Cyatheaceous/i/.y^/////^^, though it has really 

 a simple sorus,— takes an intermediate place between the Gleicheniaceae 

 and the Cyatheaceae in respect of its various characters. While G. pectinata 

 may be held as the most advanced species of the creeping genus Gleiche7iia, 

 Lophosoria is the most primitive of the upright Cyatheoids; but in many 

 features these Ferns approach one another. It has been argued at length 

 elsewhere ("Studies on Phylogeny, II," Ann. of Bot. xxvi, p. 292) that the 

 primitive Gleichenias foreshadowed the probabl)' prone ancestr)- of the 



