Parr 2, 1913] DICRANACEAE 157 
Leaf-margins more or less recurved below; capsule not strumose. 1. D. pellucidum. 
Leaf-margins flat; capsule strumose. 2. D. olympicum. 
1. Dichodontium pellucidum (L,.) Schimp. Coroll. Bryol. 
Eur. 12. 1855. 
Bryum pellucidum V,. Sp. Pl. 1118. 1753. 
Bryum flavescens Dicks. Pl. Crypt. Brit. 2:4. 1790. 
Dichodontium flavescens Lindb. Bot. Not. 1878: 113. 1878. 
Dichodontium subflavescens Kindb.; ROll, Hedwigia 35:59. 1896. 
Dioicous: male plants of the same size as the fertile and mixed with them or in separate 
tufts, the perigonial leaves from a broad, concave base rather abruptly narrowed to a lanceolate 
point with the costa vanishing below the more or less obtuse or acute apex, the antheridia 
numerous, more than 0.5 mm. long, with slender paraphyses: plants in small tufts to often 
extensive mats, yellowish-brown to dark-green, with radiculose stems 1-10 em. long, often 
bearing slender, distantly-leaved innovations from just below the apex: stem-leaves ovate- 
lanceolate or lingulate to linear-lanceolate, up to about 3.5 mm. long (or in D. pellucidum 
fagimontanum Brid. pointed-ovate or oblong and mostly 1 mm. or less long), when dry incurved- 
spreading, somewhat crispate or variously flexuous from an erect base, when moist widely 
spreading, the broad point keeled, with a rounded or acute apex and flat, not thickened margins, 
from finely serrulate to coarsely and irregularly serrate (D. pellucidum serratum Schimp.), 
the margin in the lower part of the leaf just above the base entire and somewhat farther up 
more or Jess recurved on one or both sides; costa stout, rough on the back in the upper part 
and vanishing below the apex, in cross-section near the middle showing 4 guide-cells, stereid- 
bands above and below and outer cells differentiated; upper leaf-cells rather irregular, mostly 
quadratic and slightly or not elongate, the median ones about 8 by 8-10 u, the lower leaf-cells 
toward the costa more or less rectangular, 8-10 » wide and 20-40 u long, those toward and 
in the margin nearly square, the alar cells not differentiated; perichaetial leaves very similar 
to the stem-leaves but slightly longer with a somewhat broader base: seta erect, yellowish, 
1—2 em. long: capsule oblong, from nearly symmetric and erect to curved and nodding, 1.5- 
1.75 mm. long, when dry often showing a short collum and more or less contracted under the 
broad mouth, with smooth, thick walls and 1 or 2 rows of stomata at the base; annulus none; 
peristome-teeth up to 804 wide and more than 400% high, dark-reddish, lanceolate, divided 
about one half down into mostly 2 forks, finely papillose above, more or less vertically striate 
on the outer face, from a darker, smooth, basilar membrane extending 2 or 3 rows of cells 
above the rim of the capsule and attached about the same distance below the rim; lid conic, 
obliquely rostrate, sometimes about as long as the capsule: calyptra cucullate, entire below, 
slightly rough at the apex: spores not quite smooth, 18-20 » in diameter. 
TYPE LOCALITY: Europe. 
DristRIBuTION: Labrador to New Jersey, westward in the region of the Great Lakes, and from 
Alaska and Montana to California; also in Europe. Growing in cool, damp places, mostly along 
streams, sometimes in water. 
ILLUSTRATIONS: Dill. Hist. Musc. pl. 46, f. 23; B.S.G. Bryol. Eur. pl. 50, 51. : 
Exsicc.: Drummond, Musci Am. 1/08; Sull. & Lesq. Musci Bor. Am. ed. 2. 60 (as D. pellucidum 
americanum); Macoun, Can. Musci 451, 402; Ren. & Card. Musci,Am. Sept. Exs. 355; Holz. Musci 
Acroc. Bor. Am. 101, 260. 
2. Dichodontium olympicum Ren. & Card. Rev. Bryol. 19: 74. 1892. 
Dioicous: male plants very similar to the fertile ones, bearing an inconspicuous, terminal, 
antheridial bud, with the 1 or 2 inner leaves much shorter than the outer, costate, broadly 
ovate, with a short, obtuse, rough, darker point, the 5 or 6 antheridia about 0.3 mm. long with 
few paraphyses: fertile plants in rather compact, dark-green cushions, with stems scarcely 1 cm. 
high: stem-leaves when dry more or less erect-appressed or incurved, when moist widely spread- 
ing, up to about 1.7 mm. long, ovate-lanceolate to nearly oblong-linear with a broad, mostly 
rounded apex, the margins flat all around and papillose-serrate to a little above the insertion of 
the leaf; costa stout, nearly percurrent, very rough on both sides, about 60 » wide below, in 
cross-section near the middle showing 4 guide-cells, stereid-bands above and below, and outer 
cells strongly differentiated; leaf-cells above obscure, roundish, mostly 6-7 » in diameter, 
with high papillae on both sides, the cells near the base becoming smooth and oblong or rec- 
