PART 2, 1913] DICRANACEAE 113 
11. DICRANUM Hedw. Fundam. 2: 91. 1782. 
Dioicous or monoicous. Plants varying in size from small, dense cushions to extensive 
deep mats, with usually erect, branching stems, abundantly tomentose or rarely nearly without 
radicles. Leaves lanceolate to lanceolate-subulate, mostly falcate-secund, smooth or mamillose 
or papillose on the back above, more or less subtubulose or grooved, with the margin never more 
thickened than the blade within and never revolute in the upper half; costa rather narrow (except 
in Paraleucobryum) and percurrent or excurrent or sometimes vanishing in the apex, in cross- 
section near the middle of the leaf showing usually one of three types of cell-structure; in the 
first, the cells are not greatly differentiated among themselves (homogeneous) and form a more 
or less semiterete costa; in the second, there is a median row of large, mostly thin-walled cells 
(guide-cells) with bands of much smaller, thick-walled cells on either side (stereid-cells) and 
the costa semiterete, often with ribs on the back; in the third, the costa is very broad and com- 
posed of 3 or 4 layers of cells, of nearly uniform size and thickness of wall, that extend nearly or 
quite across the leaf, the middle or middle and lower rows with more or less chlorophyl; cells of 
the leaf-blade often much thickened and pitted, the lower ones rectangular, the upper elongate 
to roundish or square with the cells sometimes in two layers; alar cells often in more than one 
layer, and forming usually a nearly square group of brown, reddish or hyaline cells usually 
not reaching to the costa and rarely auriculate. Setae erect, solitary or aggregate. Capsule 
mostly cylindric, erect and symmetric or curved and inclined, often strumose; lid rostrate; 
annulus usually present; peristome-teeth 16, inserted near the rim of the capsule, usually 
divided to the middle or below into 2, rarely 3 or 4 forks, the outer plates of the teeth mostly 
vertically striate, sometimes only papillose, rarely smooth, the inner plates mostly with very 
distinct, projecting articulations. Calyptra cucullate, smooth or papillose above, without cilia 
at base. Spores more or less rough. 
Type species, Dicranum scoparium Hedw. 
Autoicous; costa semiterete, its cells homogeneous. 1. ArRcTOA. 
Dioicous. 
Costa semiterete, its cells heterogeneous. 
Capsule erect, mostly straight. 2, ORTHODICRANUM. 
Capsule nodding, mostly curved. 3, EupIcRANUM. 
Costa broad, not semiterete, its cells morphologically homogeneous, but 
only part of them chlorophyllose. 4. PARALEUCOBRYUM. 
1. Arctoa. Autoicous; mostly small alpine species; stems bearing few or no radicles above; 
costa semiterete, excurrent, of homogeneous cells; cell-walls usually somewhat thickened and not 
pitted, or only slightly so in the lower part of the leaf toward the costa; capsule erect, not strumose, 
on a short seta 3-8 mm. long, or curved, nodding, and strumose, on a longer seta; alar cells sometimes 
forming a rather small, not very distinct group; beak of the calyptra mostly papillose. 
Capsule erect, regular or nearly so, not strumose; spores 20-28 in diameter. 
Peristome-teeth divided to the middle or below into two forks. 
Capsule about one and a half times as long as thick, exserted on a 
seta 5-8 mm. long. 1. D. hyperboreum. 
Capsule about as long as thick, not exserted above the tips of the leaves, 
on a seta about 3 mm. long. 
Peristome-teeth mostly not divided above, with short slits here and there 
about half way down. ee 
Capsule curved, nodding, more or less strumose; spores 13-16 in diameter. 
Annulus narrow, obscure; calyptra densely papillose half way down or 
more. 4. D. falcatum. 
Annulus broad, distinct; calyptra less papillose. 
Leaf-cells in the upper half of the blade mostly short, from square to 
4 times as long as broad. 
Stem-leaves less than 2 mm. long, rough above, with high, crowded was 
papillae; male flower close to the perichaetium. . 5. D. hispidulum. 
Stem-leaves up to about 4 mm. long, much smoother above, with 
mostly low, often indistinct papillae. 
Male flower some distance below the perichaetium or on a 
separate branch; leaves not distinctly secund; capsule 
NO 
. D. Anderssonii. 
oO 
. D. fulvellum. 
smooth. 6. D. Schisti. 
Male flower at the base of the perichaetium; leaves secund; - 
capsule furrowed. 7. D, Starkit. 
Leaf-cells above mostly 8-12 times as long as wide; upper stem- ; 
leaves about 5 mm. long. 8. D. arcticum. 
2. ORTHODICRANUM. Dioicous; species of medium size; costa semiterete, with mostly distinct 
guide-cells and one or two rows of smaller cells above and below, sometimes forming distinct stereid- 
bands; capsule mostly straight and erect, never strumose; beak of the calyptra smooth, 
