37 
maintained as valid: In 1889 Kindberg described in the BULLETIN 
S. aquatica var. nigrescens, which Mueller in 1890 raised to specific 
rank as S. Nevit. In Macoun’s Catalogue, 1892, another species 
was described by Kindberg S. MJuelleri, and in a recent number 
of Hedwigia Mueller described S. aguatica var catilliformis from 
Roll’s collections. This makes four species and one variety thus 
far described in the genus: 
Having had occasion to examine critically some specimens re- 
ceived from the Department of Agriculture, collected in the State 
of Washington by Leiberg and Sandberg, I found it necessary to 
see authentic specimens and original descriptions of all the species. 
These we have been fortunate in possessing either in the Torrey 
or Jaeger herbaria, where we found Lobb’s specimens of S. pata- 
" gonica, and the others have been sent us by Prof. Macoun, and by 
Dr. Watson in former years. 
As a result we have reached different conclusions from those 
of Miiller and Kindberg, and are of the opinion that S. aguatica is 
a very variable species, within certain narrow limits. That the 
forms which have been separated from it as S. Mevit, and S. Muel- 
/ert, intergrade with it is beyond question, and I have been able to 
prove that the characters which have been relied on to found spe- 
cific differences may all be found on one specimen, of either or 
any of the species distributed under the new names. There are 
some characters which seem to have been given too much weight, 
and others too little. I find that the tendency to differentiation of 
the cells bordering the leaves, runs through all the species, and 
reaches its maximum in the Patagonian specimens, by the forma- 
tion of a thick border just inside the margin, composed of paren- 
chyma cells on the upper surface of the leaf, with yellow prosen- 
chymatous cells on the lower surface like those composing the 
vein, giving the leaf the aspect of being triple-veined. In Wat- 
son’s specimens from Spokane Falls, which I have described as a 
new species, S. marginata (presumably those referred to in the 
Manual under G. Scouleri) I also find this character developed 
though in a less marked degree. The margins are bistromatic, or 
else the cells are larger and darker in color, though never as 
dense and dark, as in S. patagonica. — Specimens of S. aquatica 
var. nigrescens, also show an upward continuation of the basal 
