Britton ayant eu Tobligeance de me communiquer le No. 253 de I'exs. R. Spruce 
et un caique des dessins de Mitten pris sur le type (Quito, leg. Jameson), j 'ai 
pu me rendre compte que ma plante n'etait pas identique a I'espece de Mitten. 
Elle en est evidemment fort voisine, mais les differences que j 'ai constatees 
sont, a mon avis, assez importantes pour I'en separer specifiquement. 
Elle s'en distingue, en effet, par ses feuilles caulinaires plus petites (0.7-0.8 
mm. sur 0.2 mm. au lieu de i mm. sur 0.3 mm.) ; par le tissu plus serre (les cellules 
moyennes ont 10-12 ^ de large, celles du L. Wilsoni dittoxgnent 15-18 //); par la 
capsule brusquement contractee en un col subcylindrique plus long que le sporange, 
tandis que celle du L. Wilsoni est insensiblement attenuee en un col conique 
d'egale longueur; par I'opercule plan-convexe, non apicule, alors qu'il est conique 
chez I'autre espece; enfin par I'anneau plus eleve, les dents du peristome externe 
plus larges et par la presence de cils au peristome interne, 
Je n 'ai pas pu constater moi-meme si le peristome du L. Wilsoni est depourvu 
de cils, mais je pense cependant qu'il en est ainsi parce que Mitten n'en parle 
pas dans sa description, et surtout parce que ses dessins representent un peri- 
stome interne avec la membrane et les lanieres sans trace de cils. 
Fontaine la Mallet, France. 
NOTE ON A FORM OF POTTIA HEIMII FROM GREENLAND 
H. N. Dixon 
In 192 1 Prof. A, C. Seward, of Cambridge University, was visiting Greenland^ 
and collected a number of mosses, which he sent to me for identification. The 
bulk of them consisted of interesting but well known arctic and sub-arctic forms; 
but a Pottia from Ata, West Greenland, about 70 degrees north latitude, deserves 
special mention. The habit, the long, glossy, pale reddish setae, etc., were charac- 
teristic of P. Heimii Fuernr., but the leaves were nearly entire, obtuse, with 
the margin frequently recurved, the capsules very short and wide, the lid re- 
markably short, only very slightly rostellate, and frequently simply apiculate, 
and the capsules being then only just mature there was no indication of systyly. 
(After lying in the herbarium, however, for some months, the capsules have con- 
tracted in width and become more elongated, while the lid had become detached 
at the rim and shows constant systyly). It became clear that the moss was a 
form of P. Heimii, and the question arose to which of the numerous varieties 
of that species it should be referred. I consulted Mr. E. B, Chamberlain on the 
matter, and he very kindly went into the question with great care; but the ul- 
timate conclusion at which he and I arrived was that it could not be placed under 
any known variety. Not that it did not possess the characters of any, but rather 
that it assumed the characters of all ! Or, more accurately, that being apparently 
of an eclectic turn of mind, it had selected a salient character from one, another 
from another, while rejecting correlated characters in each; and with a true 
catholicity refused to be bound down to any single denomination! Moreover, it 
