66 
simple, growing on the threads. The only species P. albus, has 
not occurred here, it is found on stumps of fir trees. The 
affinities of the Genus are very doubtful. I have followed Mr. 
Cooke in his Handbook in placing it here. It is not creamy in 
its early stage and thus does not answer to the character of the 
Order. Corda Icones ii. f. 90. 
GENUS 80. DIDERMA.* Pp. 
Peridium double, the outer one distinct, crustaceous, smooth ; 
the inner one delicate, evanescent, attached to the flocci, with or 
without a columella. 
1.—Diderma vernicosum P. Sow. t 136. Grev. t 111, the only 
species that has occurred within our district out of 13 British 
is very common on dead twigs, &c., in the woods. 
GENUS 81. DIDYMIUM.t 
Peridium double, the outer one breaking up into little scales, 
the inner membranaceous, delicate. 
1.—Didymium melanopus /’r Bischoff t 3669. On rotten wood, 
Langridge. 
2.—Didymium hemisphericum Fr. Sow. t 12, not uncommon on 
dead leaves, &c. 
3.—Didymium squamulosum 4 & St 4f.5. On dead leaves 
common. 
4,—Didymium leucopus /’r. On dead wood, &c., Batheaston. 
5.—Didymium lobatum Nees f. 104 on moss, &c., Rudlow. 
6.—Didymium Cirereum Fry. Batsch f 169 on decaying stems, 
7.—Didymium serpula 7. Batheaston on rotting plane leaves. 
This species seems rare, as it has occurred here only once, and 
was then new to Britain, it occurred in Scotland the same 
year. 
We can only claim 7 out of 17 species recorded as British, it 
* Diderma from dis double, and derma the skin. 
+ Didymium from didumos double. 
