1922] RAYNER—NITROGEN FIXATION 229 
believed to be the endophytes associated with the different species, 
but the necessary proof was lacking, inasmuch as seedlings of the 
latter were never obtained free from mycorhiza. All attempts to 
sterilize seeds failed, since sooner or later the roots of seedlings 
raised from such seeds showed the 
mycorhizal condition typical of 
the species in nature. The five 
strains of Phoma, as well as Asper- 
Fic. Fic, 2 
Fic. 1, 2,—Fig. 1, Calluna vulgaris: representative seedlings (four months ae 
from large number grown in agar nutrient lacking nitrates; growth continued un 
fig 2, Calluna vulgaris: representative seedlings (three months old) from silica jelly 
cultures lacking combined nitrogen; silica nutrient in right-hand tube chanced 
to be more liquid in consistency than other tube, or than tubes shown in fig. 3, hence 
more vigorous root development; finer roots in upper part of root system not visible 
in photograph. 
gillus niger and Penicillium glaucum, were subsequently cultivated 
on media free from combined nitrogen. The cultures were carried 
on over a period of several years, were frequently repeated, and 
due precautions were observed with regard to purity of materials, 
adequacy of controls, and methods of estimation. It is recorded 
that none of the fungi investigated required a supply of combined 
nitrogen for healthy development or growth. They all fixed 
atmospheric nitrogen, but in very different degrees. The values 
