CHESTNUT BARK DISEASE. 427 
differ from both the latter by being decidedly narrower (see 
Plate XXVIII a-c). The ascospores of E. gyrosa are much 
nearer to the type of the true blight fungus than to E. radicalis, 
although they are somewhat intermediate. In general we can 
describe the ascospores of E. radicalis as linear, those of -E. 
Syrosa as narrowly oval, and those of E. gyrosa var. parasitica 
as broadly oval. Usually one finds some spores of E. gyrosa 
and the variety parasitica that cannot be distinguished in size 
or shape. However, upon examining many from a specimen, 
one can tell which it is, as E. gyrosa has some spores that are 
narrower, and variety parasitica some that are broader, than 
any found in the other form. 
Measurements were made of one hundred ascospores of 
Endothia gyrosa var. parasitica from ten different chestnut trees 
from various localities, and these varied from 6 to 10 mw long x 
2.75 to 5 » wide, while the average was 7.45 p long x 3.2 » wide. 
Similarly, one hundred ascospores of E. gyrosa from ten dif- 
ferent chestnut trees from various localities, including one from 
Europe, varied from 6 to 9 » long x 2 to 3.5 « wide, the average 
being 7.205 » long x 2.695 » wide. To have maintained the 
same proportion in width as in length to var. parasitica, these 
spores should have been 3.095 » wide. Likewise, sixty ascospores 
of £. gyrosa on six oak trees from different localities, one from 
Europe, showed a variation of 6-9 p x 2-3.25 w, averaging 7.099 wx 
2.733 p. Also forty ascospores of £. gyrosa on Carpinus from 
two sources in Europe varied from 5 to 10 pw Xx 2.25-3.5 pm, averag- 
ing 7.58 wx 2.8 p. 
These measurements show that there is a rather constant di. 
ference in the width of the ascospores of Endothia gyrosa and 
E. gyrosa var. parasitica, no matter what the host or the locality 
from which they came, and if we also take into consideration 
the differences in artificial cultures and in the parasitic habits 
of the two, there seems no reason for not considering the 
blight fungus at least a distinct variety. The nomenclature of 
this variety is as follows: 
Endothia gyrosa var. parasitica (Murr.) Clint. 
Diaporthe parasitica Murr. Torreya 6: 189. 1906. 
Valsonectria parasitica Rehm, Ann. Myc. §:210. 1907. 
Endothia parasitica Anders. Phytop. 2: 262. D. 1912. 
Endothia gyrosa var. parasitica Clint. Science 34:913. 
27 D. 1912. 
