ON THE STUDY OF THE MOSSES. 215 



distinctly roughened or granulated as in Hypnum rutahulum. It may be 

 straight or varioi^sly curved. 



The base of the fruit-stalk is surrounded by leaves which in some 

 species differ remarkably in both form and structiu-e from the other 

 leaves of the plant. These are the perichEetial leaves, and the character of 

 these leaves often forms a special feature in the description of mosses. 

 If these leaves are carefully removed it will be seen that the base of the 

 fruit-stalk is smTounded by a membranous sheath, the vaginula, (10 c,) 

 already mentioned; this is usually smooth, but in some species it is 

 more or less clothed with haii'-like processes, and these minute differences 

 are in some cases great aids in the discrimination of nearly aUied mosses. 



At the top of the fruit-stalk is the capsule or urn, (4 c, 5 h,) and this 

 organ presents great variety in its form, in some cases globose, Pliascuin 

 cuspidatum ; pesiVBhsLj)ed,Leptohryumpyriforme; cyhndrical, Tortula aloides; 

 straight, curved, or erect, Tetraphis pellucida, (12 ;) cernuous (curved to cue 

 side) as in Ilypiiumrutahidum, (5,) or pendulous as in many of the Bryums ; 

 it may be smooth, striated, or furrowed. 



In some species the capsule, (14 b,) is swollen all round at the base 

 (14 c,) and this swollen part is called the apophysis, as in Splachiium 

 splucricum ; this apophysis may be seen at the base of the capsules of 

 Polytrichum commune, but not so exaggerated as in Splachnum, sometimes 

 the swelling is confined to a httle bulging out of one side of the base of 

 the capsule as in Dicranum falcatum, (13 b,) or in Dlcranella cerviculata 

 or Ceratodon purpureus, &c. ; the capsule is then said to be strumose. 



The capsule is surmounted by a membranous hood called the calyptra, 

 already mentioned as being developed from the upper portion of the 

 fertihsed archegonium, (10«, 17, 18.) In some genera, such as the Bryums, 

 this hood falls away early, and hence is not seen upon the mature capsule, 

 but in many other genera, such as Tortula, Hypnum, &c., it is persistent 

 and may readily be seen. In the act of separation'from the lower part of 

 the archegonium, or vaginula, the calyptra is sometimes irregularly torn at 

 its base as in Grimmia apocarpa, or it may be evenly torn as in Encalypta 

 vulgaris. In both cases the calyptra is termed mitriform or mitre-shaped 

 (10 a.) In many other mosses it is sht up one side, and is then said to 

 be dimidiate, (Lat., dimidium, a half,) (18,) or it may be inflated as in 

 Funaria, (17,) and these characters are constant. Usually the outer 

 surface is smooth, but in some species it is papillose, and in others more 

 or less densely clothed with hairs as in Orthotrichum and Polytrichum. 



The mouth of the capsule is closed with a Uttle lid called the oper- 

 culum, (12 a, 13 a, 14 a,) and between the hd and the mouth of the capsule 

 a ring of minute, highly hygroscopic cells frequently occurs called the 

 annulus, (Lat., a ring.) The function of this ring is that of casting off the 

 lid when the spores are ripened, and thus aiding their dispersion, but in 

 many mosses, such as Tortula unyuiculata, thex-e is no annulus, and the 

 lid is then cast off by the sweUiug of the contents of the cajjsule. The 

 operculum is not always present, and here nature adopts other means to 

 bring about the dispersion of the spores ; in the Andreasas or split-mosses, 

 (19,) the capsule si^lits into four valves, (10 a,) and in the Phascums or 



