120 FISSIDENTACE/E. 



One of the smallest species, and often more conspicuous from the red tinge of the 

 setae than from the stem and leaves. Under the microscope it comes nearest in 

 structure to F. viridulus var. Lylei, but that plant always has a distinct border of 

 narrow cells to the sheathing laminae, and usually shows indications, in other parts of 

 the leaf-margin, of a similar structure, of which there is no trace in the present plant ; 

 it cannot, thus examined, be mistaken for any other species. In the field the longer, 

 red seta will distinguish it from the above plant, and from other forms of F. viridulus, 

 the erect capsule from F. incurvus, and the small size from most of the other species ; 

 F. pusillus is more difficult to distinguish, but has usually a paler seta, and more 

 numerous leaves, the uppermost pair distinctly longer. 



2. Fissidens viridulus Wahl. (Dicranum viridulum Swartz.) 



(Tab. XX. B.). 



Very small, closely gregarious, bright green. Stems longer 

 than in the last, the leaves usually more numerous, in 4-8 pairs, 

 broader, oblong-lanceolate, acute, the sheathing laminae longer, 

 inferior lamina reaching to the insertion or nearly so, nerve 

 reaching apex, leaves bordered with a very narrow cartilaginous 

 thickened margin of narrow-linear cells without chlorophyll, which 

 becomes less distinct at the apex or disappears, often giving place 

 to a few minute and obtuse denticulations. Areolation slightly 

 smaller than in the last, about 8 /j. wide. Calyptra occasionally 

 entire at base. Capsule on a short terminal seta (about 2 lines), 

 erect and symmetrical , more rarely inclined, occasionally slightly 

 unequal, oval ; lid conical-rostellate, short. Male inflorescence as 

 in the last, occasionally synoicous. 



Var. y8. Lylei. (F. pusillus var. Lylei Wils., Braithw. Br. M. 

 Fl. p. 68; F. exiguus Sull., opus cit. p. 81). Minute. Leaves in 

 3-6 pairs, less acute, border wanting except on the sheathing laminae 

 where it is usually distinct, or very faint on other parts of the leaf ; 

 capsule erect, or slightly inclined, short, oval. 



Hab. Clay banks, and rocks in shady places. Frequent. The var. /3 rare. Fr. 

 winter. 



This and the two following species are so closely allied, and are indeed separated 

 by so few, unimportant characters, that the true positions of their various forms are 

 very difficult to define, and, as has frequently been observed, it is doubtful whether 

 they should not properly be united under a single specific type. The main points of 

 difference between this and the next are the broader leaves in the present plant, more 

 or less uniform in length in the upper part of the stem, and the somewhat larger size ; 

 the inflorescence, too, is usually autoicous, while in that species the male plant is 

 generally separate from the female and thus the plant is dioicous. All these 

 characters, however, are variable. 



The var. Lylei, which is by several authors considered a separate species, is 

 remarkable for its almost total absence of border to the leaves ; I have, however, found 

 several intermediate forms growing in the same localities, and in F. viridulus, indeed, 

 the border is far from being uniform, and I have gathered specimens otherwise typical 

 in which the border in the inferior lamina becomes very narrow and almost obsolete. 

 I am compelled, therefore, to consider it as only a varietal form. The cells of the 

 var. Lylei axe, sometimes at least, slightly larger and more pellucid than in the type. 

 I do not find the lid, as Mitten describes it, longer than in F. pusillus. 



