HYOCOMIUM. 411 



double, short and faint; areolation almost uniform throughout 

 the leaf, linear-vermicular , a little laxer at base. Paraphyllia 

 present, not numerous. Seta rough ; lid conical, acuminate ; 

 peristome perfect. Dioicous. 



A genus of a single species, clearly distinguished by the wide 

 leaves with short double nerve and the rough seta. 



1. Hyocomium flagellare B. & S. {Hypnum flagellare 

 Dicks.) (Tab. LIN. I.). 



Stems elongated, 3-8 inches long, prostrate or pendulous, 

 usually simple or twice or thrice divided, unbranched below, 

 above with numerous more or less regularly pinnate and 

 complanate branches, or fewer, more elongated and parallel ; 

 branches straight or curved, often long and attenuated, terete ; 

 forming wide dense tufts or mats, of very soft texture, of a bright 

 or more frequently golden, glossy green. Stem-leaves imbricated, 

 erecto-patent, widely cordate-triangular from an excavate, semi- 

 amplexicaul base, abruptly acuminate to a fine, somewhat 

 flexuose acumen, which is often squarrose ; branch-leaves 

 narrower, more closely imbricated, less abruptly acuminate, often 

 nerveless, usually densely imbricated , rendering the branches 

 terete, sometimes secund. Leaves somewhat plicate, margin 

 plane, somewhat undulate, sharply serrate with distinct, slightly 

 squarrose teeth almost all round ; nerve double, very short and 

 faint, rarely short and single, indistinct. Cells linear- 

 vermicular, more or less obtuse, 10-15 times as long as broad, 

 the walls often porose ; at base shorter, rather wider, especially 

 at basal angles, where they are often widely rhomboid-hexagonal ; 

 but not quadrate, obscure, nor forming defined auricles. 

 Pericha^tial bracts with long flexuose points ; seta very rough, 

 hardly an inch long; capsule widely oblong, thick-walled, inclined. 



Hab. Rocks in and near streams and waterfalls, frequent. Fruit very rare, 

 autumn. 



A very variable moss, but usually with a soft, feathery habit, which with the 

 imbricated, wide leaves is sufficient to identify it ; the fruit is very rare, and the rough 

 seta — one of the most distinct characters — is not often available for determination ; 

 but under the microscope the cordate leaves with short double nerve and long narrow 

 acumen are quite distinct from those of all our mosses except Hypnum molluscuvi, 

 which, moreover, it often simulates in habit ; the angular cells of that species are, 

 however, almost always clearly defined ; the median ones usually shorter, often much 

 wider, and the leaves themselves almost always falcato-secund with more flexuose 

 points and less distinct serratures ; in the present plant the leaves though occasionally 

 secund are rarely falcately curved. In mountain streams it often becomes much 

 elongated, with long simple branches, hardly pinnate, somewhat like the similar 

 forms of Hypnum ochraceum. 



