DICRANUM. 49 



& number of species, and those frequently so anomalous in ap- 

 pearance, cannot be divided according to the principles now so 

 generally adopted by muscologists. The Fissidentes of Hedwig 

 have so remarkable a character in the form, structure, and di- 

 rection of the leaves, that we were almost tempted to depart 

 from the Linnaean rule in taking the generic characters from the 

 fructification, and to employ solely those founded on the dif- 

 ference of foliage. This, however, will form an admirable cha- 

 racter for the primary division of the species. Even in the true 

 Dicrana, many vary from what we must still regard as the most 

 essential character of the genus ; viz. the regularly cleft teeth of 

 the peristome. D. virens has the cleft often united at the apices 

 of the segments. In D. rufescens the segments are unequal : in 

 D. spurium frequently trifid. Those of D. purpureum are so 

 deeply divided that we have had no hesitation in removing it to 

 the genus Didymodon, with which it likewise accords full as well 

 in habit. Mohr cautions us to distinguish carefully between Dicr, 

 longifolium and the foreign Didymodon longiiostrum, and be- 

 -tween the likewise foreign Dicr. tortile and Didymodon homo* 

 mallum and Weissia heteromalla. This last indeed we believe^ 

 as we shall hereafter have occasion to mention, to be nothing 

 more than Didymodon homomallum, of which the peristome was 

 not sufficiently examined. But there are other true Weissia, and 

 W. acuta in particular, which bear a very close affinity to Di* 

 cra?mm. 



A. Leaves inserted in a bifarious manner* 

 (Fissidens. Hedw,) 



1. jt). Iryoides ; fruitstalks terminal; perichaetial leaves resem* 

 bling the cauline ones. (TAB. XVI.) 



. Capsule erect. 



D. bryoides. Swartz Muse. Suec. t.2.f. 4. Engl Bot. t. 625. Turn. 

 Muse. Hib. p. 53. Fissidens biyoides. Hedw. St. Cr. v. 3. t. 29. Hyp 

 num bryoides. Linn. Sp. PI. p. 1688. Dieranum viridulum. Swartz 

 Muse. Suec. t. 2.f. 3. Engl. Bot. t. 1368. Bryum viridulum. Linn. 

 Dicks. Crypt. fasc. 1. t.l.f. 5. Fissidens exilis. Hedw. Sp. Muse. t. 38. 

 f. 7-10. Dieranum osmundioides. Turn. Muse. Hib. p. 55. Engl. Bot. 

 t. 1662. Fissidens osmundioides. Hedw. Sp. Muse. t.40.f. 7-11. Hyp- 

 num asplenioides; Dicks. Crypt, fasc.2. t. 5. f. 5. Dill. Muse. t.34.f. I. 



/3. Capsule drooping. 



D. tamarindifolium. Turn. Muse. Hib. p. 55. D. incurvum. Mohr. 

 Fissidens incurvus. Schivaegr. Suppl. t. 49. Fissidens palmatus. Hedw* 

 St. Cr. v. 3. t. 30. A? Fissidens longifolius. Bridell 



HAB. Moist banks and in woods, abundant. 



This little plant has the stems from half a line to full an 



K 



