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 genera, with a costa reaching or exceeding the middle of the leaf, but 

 occasionally short and bifurcated; areolation close, cells linear, those of 

 the apex short and enlarged, those of the angles hyaline and inflated, 

 forming more or less well defined auricles. 



At present this group comprises the four following species: 

 I. Stem pinnate, leaves strongly decurrent, lightly denticulate above 

 the base, the branch leaves homotropous, auricles large, well defined, 



H. Tundrae Arnell 



1. Stem little branched or almost simple, leaves little decurrent, entire 

 none homotropous, auricles ill defined 2 



2. Leaves spreading, distant, ovate-elliptical, contracted only toward 

 the apex into a short, often inflexed acumen. H. Bakeri Ren. 



2. Leaves gradually narrowed from the lower third into a straight, not 

 inflexed acumen 3 



3. Leaves loosely imbricated, oblong-lanceolate, cells straight with 

 thin walls H. pseudostramineum C. Miill. 



3. Leaves densely imbricated, oval-lanceolate, almost deltoid; cells 

 flexuous with dense walls H. plesistramineum Ren. 



H. PSEUDOSTRAMINEUM C. Miill. A spccics very rare, and not well 

 known, habitually confounded with various forms of H. fluitans (group 

 amphibium) and of H. adunciim (groups Kneifhi and pseudofluitans) or 

 referred as a variety to one or the other of these two species. I must in 

 this connection rectify an error which I committed in the treatment of the 

 Harpidia (Muscologia Gallica. Husnot), before I had been able to examine 

 an authentic specimen of H. pseudostramineum C. Miill. I wrongly re- 

 duced this species to a synonym of H. fluitans var. pseudostramineum C. 

 Miill. According to Dr. Sanio, Carl Miiller has published in the Bot. 

 Zeitting (1855) a description of H. pseudostramineum C. Miill. Schimper 

 (Syn. ed. H. 736), who says he received from Hampe the original (type) 

 specimen of C. Miiller, places this plant in the subgenus Harpidium, with 

 the remark: " //. pseudostramineum C. Miill Ms. teste Hampe," and 

 he describes the leaves as "sharply acuminate (acute acuminata)." 



Dr. Sanio (Hedwigia. 1887, Heft IV, V,) who had in his possession 

 also an original specimen from C. Miiller, gives a supplementary description 

 of it in which he describes the leaves as " acute." 



Thanks to the courtesy of my friend Warnstorf I have recently been 

 able to examine an original (co-type) specimen collected by C. Miiller himself 

 in the type locality near Halle a/d Saale (" Dolauor Heide), in May, 1863, 

 and to establish the fact that the leaves are obtusely acuminate, which dis- 

 tinguishes this plant from all forms of H. fluitans and H. aduncum. On 

 the other hand it is completely separated from H. stramineum Dicks, by 

 several characters and also by the dioicous inflorescence. In fact it is not 

 satisfactorily referable either to the subgenus Harpidium or to Caliergon. 



H. PLESISTRAMINEUM, Rcu. A species closely related to the preceding, 

 from which it differs by its very slender, almost simple stems, by its leaves 



