407 
Groom.—‘Brown Oak ’ and its Origin. 
Penicillium . On incipient c brown oak ’ of Oliver’s and Borthwick’s 
specimens there eventually were produced small spheroidal basidiocarps 
which Mr. George Massee identifies as Melanogaster variegatus var. 
broomianus. The identity of the conidiate fungus with that of the 
basidiate one was not established by pure cultures. If, however, the wholly 
or partially subterranean species of Melanogaster in question is the fungus 
responsible, infection by hyphae or spores through a wound in or near the 
root would appear to be especially simple, and might be partly responsible 
for the preponderance of ‘brown oak ’ near the base of the tree. In this 
connexion may be mentioned the fact that the main root of ‘ brown-oak ’ 
trees is often found to be destroyed. 
That the production of ‘ brown oak 5 is not due to the direct action of 
a particular chemical ingredient of the soil is proved by the distribution of 
this wood in the individual tree as well as by the occurrence side by side 
of normal and ‘ brown-oak 5 trees. 
In conclusion I express my thanks to Professors H. Brereton Baker, 
F.R.S., and J. F. Thorpe, F.R.S., for securing quantitative estimations of 
the iron and tannin respectively, and to Mr. W. P. Rial for performing the 
analysis in the case of the latter; to Messrs. Alexander Howard and 
Stuart Oliver for valuable information ; to Messrs. Borthwick, Bradley, and 
E. T. and S. Oliver for kindly supplying fresh specimens ; and to Mr. George 
Massee for his identification of the fungus. 
APPENDIX. 
By Mr. W. P. Rial. 
Tannin in Oak heart-wood. 
The wood was taken in the form of fine shavings across the grain : 
9 grammes of this were placed in an extracting apparatus and extracted for 
i hour with 225 c.c. water. The residue was then extracted for another 
hour with 225 c.c. water, and at the end of this time a few drops of the 
liquid which was passing through the wood were tested with FeCL and found 
to contain no tannin. The extract was placed in a 500 c.c. measuring 
flask and made up to 500 c.c. 
This was done for both specimens in a similar manner. 
The tannin present was estimated by the method used at the Yorkshire 
College. 
25 c.c. of an indigo carmine solution are added to 750 c.c. H 2 0 and 
KMn 0 4 added until a pure yellow colour is obtained. 
The titration is then carried out in presence of 5-c.c. of tannin extract, 
and also in presence of 20 c.c. of pure tannin solution. 
