193 
DESCRIPTIONS OF NEW BRITISH MOSSES. 
By W. Mirren, Esa., A.L.S. 
(PLATE XIX.) 
Hypnum imponens, Hedw. Stems red, prostrate, or when closely 
` tufted ascending, irregularly pinnate with branches of uneven length, 
Leaves yellowish-green, in age becoming brown, all secund, hooked, 
ovate-lanceolate, gradually narrowed to the slender point, slightly con- 
cave with two short nerves, the margin for a short space near the base, 
recurved, and from above the middle to the point minutely serrulate, 
the cells elongated and very narrow, the alar cells small, square, well 
defined, the outer ones pellucid, those next towards the nerve deep- 
brown ; leaves of the branches narrower, with their lower margins 
somewhat plane. Phyllidia small, variously divided, brown. Periche- 
tium composed of numerous leaves, attenuated, flexuose, and serrulate 
from an ovate 2-nerved base. Capsule on a seta an inch or more long, 
cylindrical, erect or slightly curved, operculum conical, peristome as in 
H. cupressiforme, inflorescence dioicous, 
H. imponens, Hedwig, Sp. Muse. p. 290, t. 77; Brid. ii. p. 618; 
Schw. suppl. i. p. 291; Müller, Synops. ii. p. 291; Sullivant, p. 74, 
Schimper, Synops. p. 624. 
Creeping on the bare soil, and growing into matted tufts on Reigate 
Heath, Surrey. June, 1864. The female plant only. 
In general appearance, this Moss is intermediate between H. mol- 
luscum and H, eupressiforme, but it is more smooth and browner than 
the first, and its leaves are more circinate and more yellowish-green 
than those of the last, to which it is more closely allied, but differs in 
its leaves being more serrulate, the alar cells pellueid and arranged in 
a different manner, the presence of small phyllidia, and the capsule and 
opereulum are also different in form. 
Originally deseribed by Hedwig from specimens collected by Muh- 
lenberg in the United States, where the species would appear to be 
very abundant from the specimens collected by Torrey, Cooley, Drum- 
mond, and Sullivant; it has more recently been observed in a few 
places in Europe, and M. Schimper states that it has been twice 
gathered in fruit, which is produced in October in the Vosges, and in 
VOL. II. [JULY 1, 1864.] z 
