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. 

 gyrosa 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 aseospores of 

 Endothia gyrosa var. parasitica from ten different chestnut trees 

 from various localities, and these varied from 6 to 10 tt long x 

 2 75 to 5 n wide, while the average was 7.45 ^ 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 /u, long x 2 to 3.5 /x wide, the average 

 being 7.205 /A long x 2.695 it wide. To have maintained the 

 same proportion in width as in length to var. parasitica, these 

 spores should have been 3.095 /A wide. Likewise, sixty ascospores 

 of E. gyrosa on six oak trees from different localities, one from 

 Europe, showed a variation of 6-9 /x x 2-3.25 p, averaging 7.099 ^ x 

 2 -733 P Also forty ascospores of E. gyrosa on Carpinus from 

 two sources in Europe varied from 5 to 10 p x 2.25-3.5 /<*, averag- 

 ing 7.58 /* x 2.8 p. 



These .measurements show that there is a rather constant dif- 

 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. 5:210. 1907. 

 Endothia parasitica Anders. Phytop. 2 : 262. D. 1912. 

 Endothia gyrosa var. parasitica Clint. Science 34:913. 

 27 D. 1912. 



