43§ HYPNACE/E. 



other points. As regards the capsule, almost every author describes that of P. 

 sylvaticum as smooth or striated, and Husnot figures it with striae ; Spruce however 

 declared that he had never seen a dioicous plant bearing the ordinary characters of P. 

 sylvaticum, which had striated capsules, and my own observation entirely supports 

 this view. The discrepancy can perhaps be accounted for on the supposition that the 

 various authors in question have assumed luxuriant forms of P. denticulatum (the var. 

 majus Boul. ) to be the dioicous P. sylvaticum, with striate capsules ; this assumption, 

 though seemingly a bold one, is the less so from the fact that the resemblance of P. 

 denticulatum in the above forms to P. sylvaticum in foliage, lid of capsule, etc. , has 

 been very little realised until lately, most authors giving the shrinking leaves, wide 

 cells and longly-beaked lid as confined to and characteristic of P. sylvaticum, whereas 

 there is not the least doubt that they are found equally on autoicous plants, 

 belonging therefore to P. denticulatum. I am therefore inclined to think with 

 Spruce that a striate capsule has not as yet been clearly proved to be ever associated 

 with a dioicous inflorescence ; though in any case the character cannot be held a very 

 important or a very useful one, since both forms of capsule occur in P. denticulatum. 



The var. Sullivantiat supplies an additional argument in favour of uniting the 

 present plant with P. denticulatum, since it approaches the latter in the glossy 

 leaves, short lid, etc., in just those characters which are held to be the most constant, 

 as distinguishing the two, with the exception of the inflorescence. 



Specimens of the var. succulentum which I gathered at Aber, in 1892, and 

 which were verified by Boswell, have the flowers all with archegonia only, so far as 

 examined ; it appears to be only by exception, and possibly a pathological condition, 

 that the flowers in Wilson's specimens were occasionally synoicous. 



P. sylvaticum is usually found barren, but when fertile the fruit is produced in 

 abundance. 



7. Plagiothecium undulatum B. & S. (Hypnum undulatum L.) 



(Tab. LV. J.). 



Robust, in large soft spreading masses, the branches long, 

 broad flat, f rondiform, 2-4 inches long or even more, procumbent, 

 pale green or, especially when dry, almost white, hardly glossy. 

 Leaves very large, iYi-2 lines long, complanate, strongly 

 transversely undulate, when dry little altered, often flexuose and 

 incurved at the tips, widely ovate-oblong, broadest near the base 

 and thence gradually narrowed but not tapering, at apex shortly 

 and narrowly acuminate or merely acute, entire or with a few 

 denticulations at the tip, rounded at base to a narrow decurrent 

 insertion, shortly two-nerved. Cells large, linear with longly 

 tapering ends, thin-walled, 15-20 times as long as broad, at mid- 

 base becoming shorter and laxer, at decurrent angles rectangular, 

 hyaline, but not well-defined from the others. Seta long, 1^/2.-2 

 inches ; capsule large, />£--2 lines long, cylindrical, curved and 

 inclined, sometimes strongly arcuate and horizontal when empty, 

 striated when ripe ; lid conical with a rather stout and moderately 

 long beak. Dioicous. 



Hab. Damp rocks and on the ground, principally in mountain woods. 

 Frequent. Fr. summer, not common. 



A splendid plant when growing and fruiting luxuriantly, as it may frequently be 

 found in rocky hollows and wet banks in woods on our mountains ; it is perhaps 



