DICRANACEAE. 9 
as D. subpungens by competent authorities. But, on the other hand, 
D. setosum, New Zealand, Otago, leg. Hector, ex herb. Mitten, and another 
one with robust dense-leaved stems (7.e., not at all the habit of subpungens), 
have also Heteroneuron section, and vary much on the same stem in the 
strength of the nerve. In fine, the different types of nerve described by 
1 
slight taxonomic importance, must not be looked upon as representing 
clearly defined and distinct groups of species, but rather as marked points 
im an intergrading series of types of structure; in which connection it 
may be remarked that the European D. scoparium offers two of these 
types in the same leaf, the lower part exhibiting the Toxoneuron, the upper 
In examining the nerve it should be recollected that in many of the 
species it varies considerably in different leaves even of the same stem, 
and measurements of the width should always be taken from several leaves 
and at approximately the same position, preferably about half-way up the 
expanded part of the lamina 
I approached the study of this group with some expectation that several 
of the species described would be found to be insufficiently characterized, 
but I was paaaeee prepared for the rete reduction in species which Kh 
examination proved to be necessary. ere are two obvious factors lead- 
ing to an undue "hata lepligation of species—on the one hand a want of 
eae een in the value of small characters, and on the other a lack of 
owledge of the distribution of allied plants i in other oth ah 
peor Either of these factors, and most commonly both working to 
gether, are oo. for a large part of the ince! synonymy 
indispensable in bryological literature. The former factor is inherent in 
human cacao and will no doubt always be an nets one; the latter, 
on the other hand, is one capable of elimination, or at least of very great 
from perhaps distant but from a phytogeographical pomt of view closely 
connected areas, and in part through a failure to appreciate the degree 
of variability attaching to some of the already known 
This is not to depreciate the authors of man of these species. Had 
the British nies it would have been in no way to their discredit if aiey 
had described as independent species of Dicranum a woodland, richly 
fruiting, yellowish plant with strongly faleate, non-undulate leaves, longly 
subulate and sharply spinose-serrate ; a second with the leaves all erect 
and straight; a third, a lowland marsh plant with bright-green distant, 
deeply undulate, igpieediay leaves; and a fourth, an alpine rock-growing 
plant always sterile, often blackish, with erect, short, almost obtuse and 
almost entire leaves—even though in after times it was shown that all 
of these belonged to one widely spread and highly variable species, 
D. scoparium. 
And, similarly, it was hardly to be expected that Dicranoloma setosum 
.(H. f. & W.), for example, described from Lord panei a and Campbell! 
