TRICHOSTOMUM. 215 



Var. /3. elatum Schp. Tall, in large deep green tufts; leaves 

 broader, more obtuse and cucullate at apex. 



Var. y. nigro-viride Dixon (Mollia crispula var. nigro-viridis 

 Braithw.) Tall, very compact, stems very slender, dark green, 

 blackish below. Leaves small, short, narrow, concave and sub- 

 tubular above with the margins slightly incurved ; areolation 

 dense. 



Var. S. gracile Dixon (Trichostomum brevifolium Sendt. ; 

 Mollia brevifolia Braithw., Br. M. Fl., Vol. II., Suppl. p. 252). 

 Short and very slender, in dense tufts. Leaves crowded, small, 

 short, narrow-linear above from a wider base, obtuse or shortly 

 pointed, margin incurved above, hardly cucullate at apex ; nerve 

 vanishing at apex or very shortly excurrent. Perichastial bracts 

 longly acuminate, nerve excurrent. Capsule very small, ovate, 

 narrowed at the mouth • lid longly subulate- rostrate, as long as 

 capsule. 



Hab. Cliffs, walls, and banss, especially near the sea ; not uncommon. The 

 var. rare ; the var. y, Ingleboro ; the var. 5, Weymouth and Swanage {Mitten). 

 Fr. rare, spring and early summer. 



This and the next species present great difficulties to the systematist, their forms 

 being very numerous and somewhat confusing ; and the fruit, which might otherwise 

 be of help in separating them, is not at all common, and the peristome fragile. The 

 following points may serve as a guide to the student, but it must be confessed that 

 some barren forms are hardly capable of certain determination, and the examination 

 of a large number of specimens, so far from elucidating the difficulties rather seems to 

 enhance them by bringing to light more numerous intermediate forms. In the first 

 place both plants are readily known from any species of Tortula or Barbula likely to 

 be confused with them, such as T. unguiculata, by the plane margins of the leaves and 

 very obscure upper areolation ; while from Trick. Jlavovirens and Pleuroch&te 

 squarrosa they are easily known by the hyaline basal cells not extending higher at the 

 margin of the leaf than at the. nerve, but passing gradually and equally into the 

 chlorophyllose areolation. Trich. crispulum is in its typical form easily distinguished 

 from T. mutabile even with the lens by the narrower leaves with distinctly and 

 abruptly cucullate apex, by their direction which is always more erect, and perhaps 

 never distinctly spreading and recurved at apex as is frequently the case in the follow- 

 ing plant ; the basal cells are also smaller and less hyaline, and the basal margin is 

 almost always entire, rarely minutely denticulate, and never distinctly so as in 

 T. mutabile var. littorale. It is probable that bearing these points in mind the 

 student will not be likely to take plants of the true T. crispulum for any other species, 

 though it must be remembered that there are forms of this plant with the leaves 

 hardly cucullate, and others with wider leaves ; but as far as my own experience goes 

 I think it is usually safe to refer plants with narrow, tapering, erecto-patent, entire, 

 shortly mucronate leaves, and also plants with distinctly cucullate apex and entire 

 margins, to this species, even though the former have the nerve straight and not 

 upturned at point and the leaves consequently not cucullate, and though the latter 

 have wider leaves more approaching T. mutabile in outline. 



Mr. Holmes' specimens from near St. Ouens, Jersey, have the leaves toothed 

 above the base, broadly Ungulate or oblong in outline, and often decidedly obtuse in 

 apex as in T. mutabile var. littorale, while on the other hand some of them have the 

 apex distinctly, though not strongly cucullate ; this form appears to me to be more 

 satisfactorily referred to the above variety, as it was, indeed, at first named by Mr. 

 Holmes, though afterwards named by him T. crisp 



