An Eocene Microthyriaceous Fungus from Mull, Scotland. 67 
studying the leaves themselves, small fragments of the cuticle 
were detached from the rock and treated with nitric acid and 
potassium chlorate, followed, after washing, by ammonia. This 
process removes the carbonaceous matter and leaves a clear 
brown cuticle which can then be mounted in glycerine, the 
upper and under epidermis being first separated with needles. 
Some very small dark spots, which could not be seen before 
treatment, were then observed with the naked eye on the clear 
cuticle, and these proved on microscopic examination to be 
discoid bodies with a radiate structure which at once suggested 
a small epiphyllous fungus. I showed the specimens to my 
colleague, Mr J. Ramsbottom, who expressed the opinion that 
they probably belonged to the Microthyriaceae. In the subse- 
quent study of this fungus I have continually received much 
help from Mr Ramsbottom and I am greatly indebted to him 
for his advice and assistance. 
Fic. t. Slab of rock with Pityophyllum sp., a coniferous leaf attacked by 
’ Phragmothyrites. Eocene, Mull. Brit. Mus. (N.H.), Geol. Dept. no. V. 
14846. Nat. size. 
Description of the material. The discoid bodies, which are 
regarded as the ascostromata (or ‘“‘thyriothecia’’) of a Micro- 
thyriaceous fungus, occur singly, or rarely in concrescent pairs, 
on the upper surface of the leaf, and in some preparations are 
scattered over it in considerable numbers (cf. Pl. VIII, fig. 1). 
They are usually practically circular, and the largest specimen 
Series 
