Feb. 1,1921 Variations in Colletotrichum gloeosporioides 731 



Plates 13 to 16 transferred from lactose-beef agar tube. 



Plates 17 to 20 transferred from lactose-beef agar tube. 



Plates 21 to 24 transferred from oatmeal agar (mycelium). 



Plates 25 to 28 transferred from oatmeal agar (spores). 



The final notes were taken October 29, 191 7. 



Plates 1 to 4. Gray, short mycelial growth. 



Plates 5 to 8. Gray to black aerial mycelium, but in some spots there were no aerial 

 hyphae, growth confined to the medium; good spore production. The peculiar spots 

 were more or less in sector-like areas. Plate 6 showed definite sectors of black and 

 gray aerial mycelium, and in some sections the growth was confined in the medium. 



Plates 9 to 12. Almost all the plates had a good growth of gray aerial mycelium, 

 while in others there appeared sectors where the mycelium was confined in the medium. 



Plates 13 to 16. No aerial mycelium, but the growth was confined in the medium, 

 was light-colored, and was producing many spores. 



Plates 17 to 20. The aerial growth is gray, woolly; some spores produced. 



Plates 21 to 24. Gray felt-like growth covering the medium; no spore production. 



Plates 25 to 28. These plates differed from plates 21, 22, 23, and 24 in that some of 

 the plates were zoned and produced more spores. 



It is clear that there exist variations in a single strain which can not 

 be accounted for on any other ground than the effect of environment. 

 If, therefore, the differences in environment have caused these variations 

 in one year, there may be a possibility of certain environments causing 

 still greater variations which would be more or less permanent. 



EFFECT OF THE MEDIUM ON SPORE SIZE 



Spores were also measured from the different media to ascertain whether 

 the spore size had been affected. One hundred spores were measured 

 from five different media, and the mean length, mean breadth, standard 

 deviation, and probable error of the mean were calculated for five strains 

 (see Table V). It will be seen that the various media did affect the spore 

 size, but all strains were not affected alike by the same medium. While 

 it has been definitely shown that there exist different strains in Colleto- 

 trichum gloeosporioides, it also has been shown that these strains are 

 affected in growth characteristics and morphological characters by the 



medium. 



MUTATIONS 



The variations which have been described in this paper occurring in 

 the various strains of Colletotrichum gloeosporioides have been shown to be 

 due to environmental factors. Not all the variations, however, which 

 occurred during the progress of the work are thought to be due to the en- 

 vironment. These variations which were thought to be induced by some 

 factor or factors other than the environment are in this paper called 

 mutations. These mutations have kept their peculiar characteristics 

 although grown under the same conditions as the cultures from which they 

 arose. 



When the various strains were isolated in the fall of 19 16, they were 

 grown in plate cultures to study their growth characteristics. The 



