1915] COOK & WILSON—ENDOTHIA PARASITICA 349 
labeled E. gyrosa and that from STEVENS called E. radicalis are in 
reality identical. Our culture work also leads us to the same con- 
clusion. Therefore, in order to avoid confusion, we will use the 
name £. radicalis, but will in such case indicate the origin of our 
original culture. 
A careful study of our cultures indicates that we have only three 
distinct species: Endothia parasitica (American and Chinese races), 
E. radicalis (E. gyrosa and E. virginiana), and E. radicalis missis- 
Sip piensis. 
Several months were devoted to preliminary work to determine 
the most desirable medium, best methods for mixing the tannin 
into the medium, and for perfecting the technique of the work. 
The formula for the most satisfactory medium, the one which was 
used in all our work, is as follows: water 1000 cc., glucose 20 grains, 
peptone to grains, potassium phosphate (iaebacie) 0.25 grain, 
magnesium sulphate 0.25 grain. A given series of cultures was 
always made from the same lot of medium, treated with the same 
extract, inoculated in the same manner, and kept under exactly the 
same conditions. 
The difficulties arising from the use of tannin in a medium con- 
taining proteid were not overcome. The first difficulty encountered 
is the fact that commercial tannin (MERCK) is an unstable and 
variable substance. According to FiscHer (Ber. Deutsch. Chem. 
Gesells. 36: 3252. 1913), tannin is an anhydrous glucoside of gallic 
acid. This relationship makes it easily convertible by hydrolysis 
into gallic acid and related substances. It is therefore entirely 
possible that no sterile culture medium can be prepared which contains 
all the tannin unchanged. 
The usual statement that tannin in contact with proteid forms 
an insoluble precipitate has not been borne out by our work. 
Indeed, comparatively large quantities of tannin may be added to 
the agar formula which we used without changing perceptibly either 
the tannin or the proteid, so far at least as we were able to determine. 
The experiments were conducted with two lots of MERCck’s 
tannin. The first of these was already in stock at the time the 
work was undertaken. By using a to per cent solution of this 
tannin, as much as 2 per cent of tannic acid could be added to the 
