30 TETRAPHIDACE/E. 



• Order III. TETRAPHIDACE.E. 



A small order of mosses distinct (except in the single species 

 of the exotic genus Calomnium which is gymnostomous) in the 

 peristome, composed of four solid conical homogeneous teeth, 

 derived from the fission of the whole cellular tissue of the interior 

 of the lid. Plants minute and gregarious, or caespitose and 

 rather taller but slender. Leaves ovate or lanceolate, smooth, 

 thinly nerved ; areolation rounded-hexagonal. Calyptra conical, 

 mitriform, plicate. Capsule oval or cylindrical, erect, symmet- 

 rical, smooth ; annulus none. Inflorescence apical, gemmi- 

 form. 



3. TETRAPHIS. Hedw. 



The characters of the genus are practically those of the order 

 as described above, the species being all peristomate. Braithwaite 

 is no doubt right in re-uniting the two European species under 

 this genus, the characters separating Tetrodontium being hardly 

 of generic value. 



A curious feature of the genus is the presence of peculiar 

 " frondiform " leaves which appear on the protonema at the first 

 development of the moss stem ; they are more or less ligulate or 

 spathulate from a narrower base, and in T. Browniana are some- 

 times forked above, somewhat as in the fronds of the Forked 

 Spleenwort, or of the " Stagshorn " Fern; in this species they 

 are persistent ; in T. pellucida, on the contrary, they disappear 

 before the development of the stem, and have on that account 

 been overlooked. 



The solid, undifferentiated teeth of the peristome appear to 

 mark a primitive stage in the development of that organ. They 

 are quite conspicuous with an ordinary pocket lens, and are not 

 fragile nor deciduous, so that they form a ready means of dis- 

 tinguishing these plants from species of Barbula, &c, many of 

 which in the fruit and general appearance are somewhat similar. 



/Plant almost stemless, with radical frondiform nerveless leaves 3. Browniana 



(Plant with leafy stem ; barren shoots with terminal gemmiferous cups /. pellucida 



1 . Tetraphis pellucida H edw . (Mn iu m pellu cidu mL., Geo rgia 

 pellucida Rabenh. ; Braithw. Br. M. Fl.) (Tab. IX. A.) 



Plants in dense tufts, bright green above, reddish brown below, 

 \-\ inch high. Stems of two kinds, (i) fertile, simple or branched, 

 with imbricated leaves, the lower broadly ovate from a narrow 



