List of British Lichens. 
415 
genus, being split up into twelve genera, according to the practice 
of some of the earlier lichenologists. The genus Lecanora as now 
understood only contains about 80 species instead of nearly 200. 
The splitting of this genus follows legitimate lines, being based 
primarily on the characters of the spores and apothecia and 
secondarily on the nature of the thallus. Some of these genera 
were given by Crombie as sub-genera, but his divisions were not 
altogether in accord with the practice of modern lichenology, and 
have not been closely followed in the list. 
The division of Collema into three genera, Lempholemma , 
Collema (why Eucollema when it is not used in a sub-generic 
sense ?) and Synechoblastus is a legitimate one, since it is founded 
on definite differences in spore characters, but the adoption of 
Crombie’s sub-generic divisions of Leptogium as generic names, 
should have been avoided, since these divisions hardly have a firm 
basis and should only he used sub-generically, if at all. Polychidium 
muscicola is rightly separated from the other Leptogia, since it has 
quite a different aspect from any other species of the genus, or 
indeed from any other member of the Collemaceae. The authority 
for this name should have been Gray and not Fr. 
In some other cases, it would have been better to have avoided 
raising sub-genera to generic rank: thus it seems unnecessary to 
elevate Parmosticta into a genus, when the only other British 
species of Sticta has very similar characters. For a similar reason 
Agyrophora, Iouaspsis and Icmadophila seem to be superfluities. 
Physcia is unfortunately omitted from the list, all the species 
being included under Xanthoria, a correct name for fiavicans and 
the four following “ Physcias,” with a yellow thallus and simple, 
colourless spores, but incapable of accommodating the other 
nineteen species (Nos. 249—267 in the list) with grey or brown 
thalli and 1-septate, dark-coloured spores. 
The species of Cladonia are arranged almost exactly as they 
were by Crombie ; it is to be hoped that this genus will receive 
drastic treatment in the revised edition of the first part of the 
British Museum Monograph, the confusion and overlapping being 
almost as great as amongst the Lecideas and Lecanoras. Cladonia 
lutco-alba with red apothecia ought not to be included in the 
Phaeocarpae, and C. Lamarkii forma Isigynii is undoubtedly the 
same plant as C. pityrea forma hololepis , as far as one can judge 
by the descriptions and plants referred to them. C. delicata seems 
to be a form with the leaflets more or less granulato-Ieprose at the 
