XXXIX] THE CENTRAL GYMNOGRAMMOIDS 75 



into coenosori does not shake this conclusion, since such fusions occur 

 homoplastically in a plurality of phyletic lines. 



II. The Central Group of Gymnogrammoid Ferns 



Under this head are included Gyjunogranimc Desv., together with the allied 

 genera. P terozoniievi Fee, Syjigrannne]. Sm., Anogramme Link, Coniograimne 

 P^ee, Heviionitis L., Ceropteris Link, and Trisnieria Fee. The genus Gym- 

 nopteris Bernh. is also included in Christensen's Index (p. xxxviii). These 

 are Ferns of moderate size and wide distribution, varying in habit, and 

 particularly in the outline of the leaf They all bear dermal scales, especially 

 upon the rhizome and leaf-base. They have for the most part a relatively 

 primitive stelar structure, but the leaf-trace is commonly divided into two 

 equal straps. Their most marked common feature is that the sorus, which is 

 without any true indusium, is spread in varying degree along the length of 

 the veins, but without extending to the actual margin of the blade. Since the 

 venation is in many of these Ferns open, and in others closed, the sori are 

 often linear as in Gymnogramme. but sometimes reticulate as in Syngramme 

 or Hemionitis. The latter state appears as a natural sequel to the expansion 

 of the blade, and may be held as derivative. The sporangia are of the ordinary 

 Leptosporangiate type, with a vertical annulus, but without specially long 

 or thin stalks. The spore-output, so far as ascertained, appears to be the 

 normal 48 to 64. The spores are often large, and spherical-tetrahedral in 

 form, and are without perispore. 



The peculiar perennation of the gametophyte in Anogramme, combined as 

 it is in y^. leptopJiylla with the unusual condition of an annual sporophyte, has 

 already been described (Vol. I, p. 276, Fig. 267). The facts point to a special 

 seasonal adaptation rather than to any line of comparative argument. 



The stelar system of them all is based upon the solenostele, and is without 

 medullary strands. It is marked by perforations, the most frequent of these 

 being a long slit which divides the leaf-trace down to its base into two straps. 

 This is seen in a relatively simple form in Gymnogramme {Ceropteris) 

 calomelanos (L.) Und. (Gwynne-Vaughan, Sol. Ferns, II, Fig. 9): but it 

 appears also accompanied by numerous other perforations in the more highly 

 disintegrated system of Gymnogramme iConiogramme) japonica (Thunbg.) 

 Diels (see Vol. I, Fig. 160), which is a species of large size. 



There will be no need to enter here into a detailed description of the 

 several genera. But as Trisnieria trifoliata has recently been examined in 

 some detail by Dr J. McL. Thompson (647), that Fern though somewhat 

 specialised may be taken as an example of the central group. The result of 

 Dr Thompson's enquiry was to conclude that Trisnieria need not be 

 considered as a genus distinct from Gymnogramme, so alike are they in 

 essential features. 



