240 Systematic Paleontology 



specimens described by Heer justify the reference of these forms to the 

 modern genus Asplenium. 



The most recent diagnosis is tliat by Seward, which may appropriately 

 be quoted for the American Cretaceous forms : 



" Fronds pinnately divided, pinnae spreading, lobes or pinnules at- 

 tached by the entire base or slightly auriculate, acuminate, or obtuse, 

 occasionally dentate, especially at the apex, not rarely subfalcately curved 

 upwards, midrib strong at base, and towards the summit dissolving into 

 branches, secondary veins given off at a more or less acute angle, 

 dichotomous a little above the base, and repeatedly dichotomous."^ 



Much difference of opinion has prevailed regarding the unity and the 

 systematic position of the genus, Saporta ^ having long ago pointed out 

 that Brongniart's Paleozoic species had nothing in common with those 

 of the Mesozoic, and that the Liassic and Oolitic forms, those which the 

 former author was discussing, give evidence of common characters. At 

 the present time there is still lacking evidence from such fructified 

 remains as have been discovered of close relationship between all of the 

 various species of Cladoplilehis. Thus Heer discovered in the Siberian 

 Jurassic fragments of the Cladophledis whithyensis type with soral char- 

 acters which he compared with those of the subgenus Diplazium of 

 Asplenium,^ and Schenk has figured fertile pinnules of the same type in 

 the case Of the allied Asplenites rcesserti.* Certain specimens of the 

 Jurassic species CladopMeiis lohifolia show that the sporangia in this 

 species were apparently borne in semi-circular pocket-like depressions 

 on the edges of the fertile segments,'^ while the fructifications of Clado- 

 pTilebis denticulata are in the form of narroAv, oblong sori parallel with 

 the secondary veins, and are compared by Seward" with the modern 

 forms Asplenium luguhre and Phegopteris decussata. In his latest utter- 

 ance on this subject he asserts that " there are fairly good grounds for 



^ Seward, Wealden Fl., pt. i, 1894, p. 88. 



^ Saporta, Pal. France, ser. ii, Vegetaux, PL Jurass., t. iv, 1888, p, 357. 



^Heer, FL Foss. Arct., Band iv, 1877, p. 38, pL xxi, figs. 3, 4. 



* Schenk, FL Foss. Grenz. Keup. Lias., 1867, p. 51, pi. vii, figs. 7, 7a. 

 » Seward, Jurassic FL, pt. i, 1900, tf. 23. 



* Seward, loc. cit., p. 141. 



