REVUE BRYOLOGIQUE 41 



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D. pellucidiim var. ereclum by Husnot [Muscol. Gall., p. 428). This 

 has the vegetative characters of B. pellucidum except that the 

 leaves are strongly serrate at margin ; the capsules are erect, 

 oblong and symmetrical as in D. flavescens, but the peristome is 

 entirely that of D. pellucidum. 



In 1897 and i898 I collected numerous forms of Dichodontium 

 in the mountains streams of Perthshire, two of them being of 

 special interest. One fruiting plant in dark green tall tufts from 

 near Lochay Bridge, Killin, revealed a most unexpected combina- 

 tion of characters. The habit, leaf characters, and erect oblong or 

 subcylindrical capsules (very rarely slightly inclined) were exac- 

 tly those of D. flavescens, and it was a great surprise upon put- 

 ting it under the microscope to find that the peristome was that 

 of typical D. pellucidum. 



A plant gathered the next year at Tyndrum was even more sub- 

 versive of the slaius quo. Two forms occurred ; in the one, which 

 I number 103, the yellow colour, the habit, and the quite erect, 

 subcylindrical capsules, brought it even nearer to typical D. flaves- 

 cens than the Lochay Bridge moss ; but here again to my surprise 

 the peristome turned out to be that of D. pellucidum. 



The second form, numbered 104 in my herbarium, was greener 

 and so far a little less like J), flavescens, but the peristome while 

 on the whole nearest B. pellucidum, showed — and. this is the only 

 instance known to me of an intermediate form of peristome — a 

 distinct approach to that of D. flavescens in the more irregular, 

 narrower teeth, only showing very faint but still distinct traces of 

 vertical stria?, while almost of the deep red colour of />. pelluci- 

 dum. 



A close examination of these and other plants has led me 

 reluctantly to the conclusion that D. pellucidum and B. flavescens 

 are connected by an almost unbroken series of inlergrading forms, 

 both as regards the oophytic and sporophytic characters. It will 

 perhaps be best to refer briefly to some of these plants m support 

 of the above statement, arranging them so as to show their rela- 

 tionship to the extreme forms. 



1. — B. pellucidum type. 



2.— Glen Dubh, Inchnadamph, Sutherland, July 1899; leg. 

 Nicholson, Salmon and Dixon, N" 123. Tall. Leaves having the 

 structure oi pellucidum, but longer than in the typo, and occasio- 

 nally spreading and merely flexucse when dry, though usually 



curled and incurved. Sterile. 



3. - Quiraing, Skye, 1893 ; leg. H. N. D. Habit and colour of 

 flavescens. and leaves variable in structure (leaf-base, papillee, 



