POROTRICHUM. 371 



branches forming a dark dull green terminal head ; branches more 

 or less turned to one side, frequently somewhat complanate, 

 slender, short and curved or longer, straighter and flagelliform ; 

 lower stem-leaves scale-like, increasing in size upwards, broadly 

 triangular and scariose, the upper more chlorophyllose ; branch- 

 leaves narrow, elliptic-oblong, narrow ed at the insertion, sharply 

 and coarsely toothed, especially above, acute but not acuminate, 

 margin plane ; all strongly nerved to just below the apex ; 

 somewhat spreading when moist, loosely imbricated when dry, 

 not twisted, but often incurved at apex so that the branches 

 appear somewhat catenulate. Areolation of stem-leaves shortly 

 elliptic, somewhat elongated and enlarged at base ; of branch- 

 leaves rounded or sub-quadrate , a little elongated at the very 

 base. Perichaetial bracts oblong-acuminate, the points divergent. 

 Seta short, about half an inch, curved at the summit, so that the 

 capsule is inclined or horizontal ; calyptra large ; lid longly 

 rostrate, oblique; capsule oblong, curved, reddish; peristome 

 large, pale red. Dioicous. 



Hab. Shady woods, and rocks by waterfalls. Common. Fruit rare, autumn. 



This fine moss is usually recognisable at once by its dendroid stems, the lower 

 part black with silvery triangular leaves ; the terrestrial form differs considerably 

 from the rupestral one ; in the former the branches are not complanate, usually curved 

 and rather robust with the leaves more spreading ; in the latter they are generally 

 distinctly complanate, straighter, more slender and flagelliform, with smaller more 

 appressed leaves. The former is more rarely found in fruit, but the capsules when 

 present seem to be larger and better developed. Numerous setse are as a rule 

 produced on each stem, and all from the summit, often very close together. 



The nerve is somewhat channelled above at back and sparingly toothed. It is 

 strong, but never occupies any considerable proportion of the width of the leaf as in 

 the next species. 



2. Porotrichum angustifolium Dixon (Thamnium angusti- 

 folium Holt, Journ. of Bot., 1886, p. 65). (Tab. L. C). 



Very small ; leaves much narrower (those of the branches 

 ligulate) , widest at the insertion, more strongly toothed ; nerve 

 very wide and thick, occupying % width of leaf at base or more ; 

 cells more elongated and narrower, especially at base and near 

 the nerve ; upper somewhat larger than in the last, irregularly 

 oval. Fruit unknown. 



Hab. By calcareous springs, Raven's Dale, Derbyshire (Holt). 



Quite distinct from the last species, and only known at present from the above 

 locality. The leaves are always widest at, not above, the base, the nerve much 

 broader, the upper cells larger. 



