286 MESOZOIC FLORAS OF FM IFD STATES. 



surpii-^ino;ly small. From the collections made in the Great Falls coal 

 field that I have examined I get the impression that this feature is char- 

 acteristic of the flora of that field also, for apparently even large collections 

 yield only a few species, these having many specimens. I find here 

 again illustrated a fact observed before: I have noticed that any layer 

 that contains a large amount of Equisetum shows very little of other 

 identifiable plants. Equisetum, in some of the layers of shale from the 

 Geyser locality, is exceedingly abundant, and in the same layer other 

 species that can be made out are rare. 



DESCRIPTION OF THE SPECIES. 



PLvlum I^TERIDOP'HYT^ (Ferns and Fern 



^-Vllies). 



Order FILICALES (Ferns). 



l^^amily CYATHEACE.E. 



Genus DICKSONIA FHrriticr. 



DiCKSQNIA MONTANENSIS FonttlillC U. sp. 



PL LXXI, Figs. 1-4. 



Of this plant on!}- fructified forms were found. The frond was 

 probably tripinnatifid at least, as the largest portions found seem to 

 be pinnae belonging to larger parts of the frond. The rachis of the 

 principal pinnae seen is comparatively stout and rigid, and in the less 

 modified foi-ms, such as are depicted in PI. LXXI, Fig. 1 (of which an 

 enlarged piiniule is shown in Fig. 2), is almost winged l)y the decurrent 

 leaves of the ultimate pinna\ The pinnte of the ultimate order vary 

 somewhat in the degree of their modification to assume the fertile form. 

 Some, as the specimen figured in PI. LXXI, Fig. 1, seem to be more 

 foliaceous and less metamorphosed. These are the broadest forms that 

 wei'e found. They are decurrent on theii- lower side so as almost to 

 foi-m a wing on the principal rachis. The lower lacinitr next to the 

 pi-incipal rachis are more united and more foliaceous than the upper ones 

 and appear to haA-e tlie sori less well developed. These pinnae go off from 

 the main rachis at an angle of about 45° and then tui-n strongly away 

 from it, so as to stand nearly at right angles to it. They are oblong- 



