— 30 — 



direction. For the present I shall exclude from Hymenostomum the several 

 tropical North American species which have been assigned to it. It is of course 

 well known that Lindberg^'^ proposed a synthetic genus covering all the above 

 and others under the name of Mollia Schrank/^ which has been followed by a 

 number of authors, notably Braithwaite^^ and (with the separation of Tricho- 

 stomum including Tortella) under the name of Weisia by Dixon, though the 

 latter in his later studies in exotic mosses seems to have broken with his earlier 

 system.2^ There is something to be said in favor of Lindberg's genus, but perhaps 

 less in favor of its name.^^ At any rate it does not apply to the more limited 

 group which I have included under Hymenostomum. Some of the groups within 

 Lindberg's genus are not however, connected by close transitional forms and 

 their separation as genera seemingly abundantly justified. It may be noted 

 that Lindberg's subgenus Hymenostomum of his genus MolliaP corresponds 

 exactly with the genus Hymenostomum as I have delimited it. 



A further case of unnatural synthesis is found in the inclusion by Brotherus^^ 

 of the genus Tetrapterum Hampe consisting of a species each from South Africa 

 and Australia with Astomum. Jaeger in his treatment of the cleistocarpus 

 mosses^^ regarded the two species as cleistocarpous relatives of Hyophila Brid. 

 They suggest to me rather relatives of species of the Trichostomum type and not 

 too closely related to each other. A would-be natural system that separates 

 generically even European Astomum and Hymenostomum can certainly not with 

 any claim to naturalness include Tetrapterum with Astomum. 



As to the valid name of the genus as we have delimited it, Weisia or Veisia 

 Hedw., 1782^^ is antedated by Weissia Ehrh., 1779^ and must accordingly be 

 dropped. The next available is Hymenostomum R. Br., 1819,^^ which also has 

 the merit not possessed by the later Astomum Hampe, 1837^^ that there is no 

 question as to its type-species, it having been proposed as monotypic (for Gymno- 

 stomum microstomum Hedw.). The question of the appropriateness of the name 

 for all species may be raised, but is not validly pertinent. In the necessary 

 transition from the old artificial grouping to something that is intended to ex- 

 press natural relationship it is inevitable that generic names originally descrip- 

 tive should cease to be distinctively so, nor is there any occasion to worry unduly 

 over the matter. We do not require all Smiths to be workers in metals or else 



"Utkast til] en naturlig gruppering, apf. 1878. 

 isBaier. Flora, II, 45s. 1789. 

 isBritish Moss Flora, I, 228ff. 1887. 



20Handbook of British Mosses, 203£f. 1896; ed. 2, 223f¥. 1904. 



2iCf. e. g. Joiirn. Linn. Soc, Bot., XLIII, 307. 1916: Gyroweisia. 



22This question is discussed at length by Lejolis, Rev. Bryol., XXII, loff. i895. 



23Musci Scand., 21. 1879. 



240p. C!t., 384f. 



25Mu'5ci Cleistocarpi, 26f. 1869. 

 ^fiFundamentum, II, 83: Weisia; 90: Veisia. 

 2'Hannoverisches Magazin, XVII, 1003. 

 28Trans Linn Soc, XII, 573- 

 2^Flora, XX, 285. 



