202 



acute or bluntly pointed ; spores minutely papillate. •' Involucel- 

 lum " of the sporogonium foot well developed. (Name from 

 Xopb(;, twisted, and dopa, door.) 



Gyrothyra Underwoodiana. 



Dioicous. Plants rather large, i-2 cm. long, 2-4 mm. wide, 

 mostly in compact light green tufts; stems creeping, thick, often 

 slightly flattened dorso-ventrally, .5-.65 mm. in diameter, about 

 15 cells wide in cross section, very densely radiculose, slightly 

 ascending at apex, subsimple or with a few irregularly disposed 

 lateral branches, in female plant innovating from near base of 

 perigynium ; root-hairs long, nearly colorless or of a dilute yel- 

 lowish-brown hue, sometimes tinged proximally with purple, 

 springing in older parts of the stem from oblong or linear dark- 

 purple callosities, made up of the closely coherent root-hair bases 

 and of other ventrally elongated cells ; leaves obliquely inserted, 

 lingulate or oval, succubous, rather close, translucent, alternate, 

 scarcely decurrent dorsally, often crowded and suberect at stem 

 apex, marginate, commonly concave below, apex decurved, 

 1.4-2 mm. X 1-7-4 mm.; cells of the margin quadrate or ob- 

 long, equalling in size the adjacent or twice as large ; other leaf- 

 cells mostly quite regularly pentagonal or hexagonal, 25-70 /i in 

 diameter, oblong and larger towards the base ; all with conspicu- 

 ous trigones; under-leaves free, often wine-colored, .6-1 mm. long, 

 bifid ]/2-j4, the length into narrowly lanceolate or subulate seg- 

 ments, usually running out into a single series of cells at apex, 

 concealed by the dense mat of root-hairs, except in the younger 

 portions of the stem; perigynium tubular, i-i}4 mm. in diameter, 

 and, with the free portion of the perianth, 3-4 mm. long, erect or 

 ascending, nearly at right angles with the stem, tinged with pur- 

 ple ventrally, bulbous or saccate at base ; wall of perigynium- 

 tube 5-20 cells in thickness ; involucral leaves 2-4 pairs (com- 

 monly 3 pairs), entire or repand, similar in form to the cauline, 

 margins approximate at base dorsally, distant ventrally ; upper- 

 most pair inserted at about middle of perianth-tube or, more 

 rarely, at two-thirds its height, erect, apex and dorsal margins nar- 

 rowly reflexed and exposing the perianth, or closely appressed and 

 wholly concealing it ; next lower pair usually inserted at about 

 one-third height of perianth-tube, more broadlv reflexed ; the one 

 or two basal pairs but slightly attached to perigynium ; involucral 

 underleaves inconspicuous, sometimes subentire and slightly ad- 

 herent to base of involucral leaves ; bulbus of perigynium with- 

 out radicles, but a dense tuft of root-hairs springs from the stem 

 just back of the bulbus and long root-hairs come from the cells 

 of the involucral leaves near their bases ; perianth free for ]A,-y2 

 its length, free portion nearly echlorophyllose, subtubular, some- 



