108 DICRANUM UNDULATUM. 



you sent I should think must be interesting, and though possibly 

 cl priori open to some question, ought to serve to draw attention 

 to a little-understood plant. There are some slight inaccuracies in 

 phraseology; for one I would presume he means " spermatozoids" 

 when he writes " zoospores," for they are physiologically and 

 functionally distinct things. According to the " priority- laws " it 

 would seem that this plant should pass rather as Hydrogastrum 

 g r a i u datum (Linn.) Desv. than as Botrydium argillaceum (Wallr.). 

 ■ — Hydrogastrum has priority over Botrydium, but the latter name 

 is often employed in algological works, apparently without due 

 regard to that circumstance. 



DICRANUM UNDULATUM {EHRHART). 

 By R. Braithwaite, M.D., F.L.S. 



This may now with certainty be entered as a member of our 

 Moss- Flora, Prof. Lindberg having detected it in Mr. Spruce's 

 herbarium. Having recently paid a visit to that gentleman, he 

 kindly gave me some of his original specimens, and informed me 

 that he found it in August, 1842, growing in dryish sand-pits in 

 a fir plantation on Stockton Forest, near York, and although speci- 

 mens were sent to the late Mr. Wilson, it has no place in his 

 " Bryologia Britannica." My friend Mr. Anderson, of Whitby, 

 has found it again in the same locality a few weeks ago, and it is 

 probable that it occurs in many other places, but, being barren, has 

 not been distinguished from D. scoparium or D. Bonjeanii; at 

 least, this is much more probable than that such a widely diffused 

 Continental and American species should be totally absent from 

 Britain. 



Mr. Spruce informs me that it is not uncommon in the lower 

 Pyrenees, growing in grassy glades of sandy woods. 



D. scoparium is at once separated by its non-undulated leaves, 

 and we may indicate the other two by the following diagnostic 

 characters. 



Die. undulatum. Ehrt.— PL Crypt, exsic, 271 (1791),. Bryum 

 rugosum, Hoffm.Deutsch.Fl. ii.p. 39 (1795). Die. poly setum, Swartz. 

 Muse, Suec. p. 34, t. iii. f. 5 (1798). 



Seta3 aggregated ; stems naked and decumbent at base ; leaves 

 patulous, the uppermost somewhat falcato-secund, .or appressed 

 and slightly secund, from a broad oblong base, lanceolate, gradually 

 narrowed into a dagger-shaped point, ending somewhat abruptly 

 in the acute apex, beautifully undulate in the upper half, carinate ; 

 margin revolute below, coarsely serrate above, the teeth spinulose 

 and somewhat irregular in direction ; nerve flattened, narrow and 

 extended to apex, narrowly two-winged and serrated at back ; cells 

 elongate-oblong or elongate-hexagonal, those of the central base 

 subquadrate and hyaline. 



