and Adiantum pe datum. Asplemum ruta-muraria has sent out a 

 few fronds, and A. trichomanes survives. The rare A. viride, A. 

 parvulum, Woodsia glabella, and W. hyperborea languished and 

 died. Phcgoptcris Polypodioides. a small ostrich fern, and 

 Xcphrodium fragrans are trying to get ahead, but with little suc- 

 cess. The latter is very fragrant. 



A number of other species, including some greenhouse ferns, 

 have been tried in previous years. Xo "management"' is necessary 

 except what is stated above, only we are often obliged to cut out 

 handfuls of fronds of some species to keep them from crowding 

 the others out of existence. 



Baltimore, Md. 



THE GENUS EQUISETUM IN NORTH AMERICA. 



By A. A. Eaton. 



TWELFTH PAPER. 

 The Sub-genus Hippochaetae Milde. 

 Stems evergreen in whole or in part ; normally unbranched 

 (in ours), very variable in size, usually well covered with silex, 

 either as a coating or in bands, tubercles, rosettes, etc. Stomata 

 in a single regular row on each side of the ridges (in ours, with 

 rare exceptions), sunk below the surface and covered by the 

 silex coating, having access to the air through a small hole over 

 each. Species mostly closely related and often difficult of de- 

 termination. 



While among the Equiseta there are no true varieties with 

 the possible exception of Arvense boreale; the Hippochaetae con- 

 sists of a multitude of races, of which the species as understood 

 are centers of variation. The system obtaining in Europe is and 

 has been to make species out of the connecting links, but a careful 

 study of a large series of both our forms and theirs has con- 

 vinced me that they are best treated as varieties. 



E. variegatum Jesupi, and E. trachyondon, for instance, are 

 almost exactly between variegatum and hicmalc, and could pro- 

 perly be made varieties of that species. Variegatum concolor is 

 exactly between variegatum and laevigatum, and but for other 

 varieties with occasional rounded angles would be considered i 



