46 ME. W. MITTEX — BEYOLOGIA OE THE STTEVEY 



nor would they be distinguishable from the others except by their 

 leaves. The capsule of H. pilifera and H. vmberlis is plicate 

 when old, but this character is observable in H. Humboldtii, Hook., 

 which is considered by M. Schimper to present distinctions suf- 

 ficient to constitute another genus, Harrisonia, and, according to 

 him, to be placed amongst the pleurocarpous mosses ; but there 

 is no real difference in the position of the fertile flower in any of 

 the species ; and the distinctions upon which these genera have 

 been propounded, when considered in connexion with those 

 existing between the species of eminently natural genera, such as 

 Orthotrichum and Fissidens, seem to be merely specific. The 

 original position of the fertile flower appears to be terminal on 

 the branches, which, producing innovations from immediately 

 below it, render it apparently lateral in the more branched 

 species. 



Among the species included in the genera Hedwigia, Hed- 

 tvigidium, Braunia, and Harrisonia, there is the closest affinity 

 in the structure of the leaves and in the mode of growth, except- 

 ing that H ciliata is destitute of flagelliform branches. In the 

 form of the capsule there is considerable diversity ; in Hedwigi- 

 dium and Sarrisonia it is short and plicate, in Braunia it is 

 elongate and smooth. In all these genera the calyptra is elongate 

 and cucullate, in Hedwigia it is short and mitriform ; but the 

 value of the genera distinguished by these characters is destroyed 

 when compared with other groups of species forming the most 

 natural genera, OrtliotricJium and Grimmia. In the first there is 

 as great a diversity in the form and plication of the capsule, and 

 in the second as much difference in the calyptra of species in 

 most other respects so very closely resembling each other, that 

 more confusion would arise in dividing them on the strength of 

 that character alone than in leaving them together. The distinc- 

 tions therefore between the Hedwigice, measured in comparison, 

 are rather of a sectional and specific nature than generic, and the 

 mere multiplication of genera serves no useful purpose. 



The position of the species composing the group here under- 

 stood as Hedwigia has been variously estimated by authors. 

 Miiller places them amongst his Hypnoid mosses, H ciliata in 

 his JPilotricJium, and the residue in the section Pterygynandrum of 

 his interpretation of the genus Nechera. Schimper places them, 

 excepting H. Hwnboldtii, between his families Grimmice and Bty- 

 chomitrice ; but the affinity between some forms of Grimmia and 

 Hedwigia ciliata is less than that existing between the flagelli- 



