DESCRIPTION OF SPECIES— EQUISETACE^. 69 



Equisctum Itl^yoining^cuse, Lesqz. 



Plate VI, Figs. 8-11. 



Equisetum Wyomingensc, Leeqs., Annual Report, 1873, p. 409. 



Stems or rbizomas equally distinctly striate, articulate; articulations short; sheaths acutely den- 

 tate ; radicles in buudles from the articulations. 



The specimens are large slabs of very hard white shale, covered with a 

 profusion of fragments of the same plants, rootlets, rbizomas, stems crushed, 

 pressed together, and rarely separated distinctly enough to clearly show their 

 characters. The best ones are figured. They represent fragments of stems, 

 or of rbizomas, articulated, slightly narrowed at the articulations, which are 

 close, either naked or marked by round small scars, and bearing bundles of 

 simple rootlets, diverging starlike ; all the fragments of stems and rbizomas 

 are equally and regularly striate; the sheaths, as seen in figs. 8 and 9, equally 

 dentate on the borders, and short; fig. 11 is apparently an inflated articula- 

 tion of arhizoma or tubercle, bearing at one end a compound branch or root- 

 let, with a whorl of rootlets in the middle; these rootlets are all of the same 

 size, less than one millimeter thick, linear or filiform, simple or forking, as 

 seen on the lateral branch of fig. 8. The stems and rbizomas, also of equal 

 size, average half a centimeter in width. 



Habitat. — Three miles east of Green River Station, Wyoming Territory. 



Bquisetum limosuin!, Linn. 



Plate VI, Fig. 5. 



Equisetum liniosum, Linn., Annual Report, 1871, p. 299. 



Stem simple, deeply striate, articulate ; articulations short ; sheaths short, acutely dentate. 



Though it is not possible to prove identity from a mere fragment of 

 Equisetum representing only part of a stem and its sheaths, it is also impossi- 

 ble to find a point of difference in comparing this stem with that of the living 

 Equisetum limosum. As in this last species, the stem is equally ten-ribbed 

 or deeply striate, the sheaths of the same length, blackened also in the upper 

 border, with narrow, acutely pointed, equal teeth, appressed upon the stem. 

 It is evidently different from the former species by the more numerous and 

 narrower teeth of tlie sheath. 



Habitat. — Near Yellowstone Lake, among basaltic rocks. The geo- 

 logical age of the formation is not indicated with the specimens; it may be 

 some recent deposit by hot springs or volcanic agency (Dr. F. V. Hayden). 



