— 3 — 
tana. In Europe and Asia it shows similar northern tendencies, occurring, 
however, in high motintain stations southward to the Alps. In Norway I have 
seen it on wet rocky mountain sides well up toward the tree-line or above it. 
14. Sphagnum riparium Angstrom, 1864. The record of this species is less 
clear than that of the one preceding, as it has, on the one hand, acquired a couple 
of European synonyms: S. speciosum (Russow) Klinggraff, 1872, and S. specta- 
hile Schimper, 1876; while, on the other, many European bryologists have refused 
to accord it specific recognition, treating it usually as a variety of S. recurvum. 
It seems now, however, to be generally recognized and well defined, except that 
Limpricht as late as 1901 1 insisted upon a division into S. riparium and S. 
speciosum on the basis of a difference in the cortical cells of the stem together with 
one or two other characters. Against this procedure Warnstorf 2 took a vigorous 
stand, nor has it appealed to other botanists. The plant is quite distinct from 
the preceding in a number of characters, many of which have already been re- 
ferred to: it normally lacks brown pigmentation; the branch-leaves when dry 
show strongly recurved tips, these tips when examined under the microscope 
displaying regularly a suppression of the empty hyaline cells in favor of uniform 
narrow cells with pitted walls; the pores in the side-regions differ de- 
cidedly, as will be described directly; the stem-leaves do not show extensive 
laceration, but have the membrane of the hyaline cells resorbed mostly on the 
inner surface, except as a resorption on the outer surface also in a limited middle 
apical part leaves the leaf with a characteristic longitudinal rent running inward 
some distance from the apex; most striking of all is a complete difference in 
stem-section, the present species showing cortical cells so similar to those next 
within that the cortex is usually spoken of as undifferentiated. This assimilation 
of cells is, be it said, a mutual one, in that not only are the cortical cells much 
longer, narrower and with thicker walls than usual, but the cells next within 
appear of greater diameter than usual, and, at any rate, do not have the very thick 
pigmented walls found in S. Lindbergii and in many other species. In this ap- 
parent homogeneity of stem-cells in S. riparium and the species most closely 
related to it I see no necessary reason to assume a primitive condition for Sphag- 
num , but rather the contrary. S. riparium is anyhow not very closely related to 
S. Lindbergii and it is rather from 5 . recurvum , which has the same condition 
of stem-cortex, that its distinction presents difficulties. These are not, however, 
great. Even where the two are growing together, a rare case represented in 
Eaton and Faxon’s exsiccata no. 84, which, in the two sets now accessible to me, 
shows a good deal of 5 . recurvum and much less 5 . riparium , the plants of the 
two species can in the dry state be distinguished at once by the naked eye. The 
branch-leaves of S. riparium give the branches a characteristic turgescent effect, 
while the tips of the leaves appear very small by contrast and are simply strongly 
recurved without the leaf being undulate. In 5 . recurvu?n, on the other hand, 
the leaves are strikingly undulate except in the small-leaved variety which could 
hardly be confounded with S. riparium. If the leaves are examined individually 
1 Rabenhorst, Kryptogamenflora, IV, 3 62ifT. 
2 Kryptogamenflora der Mark Brandenburg, I, 362f. 1903. 
