228 BOTANICAL GAZETTE [MARCH 
The experimental evidence in question is derived from three 
sources. (1) The work of TERNETZ,3 who showed that certain 
fungi isolated from the roots of ericaceous species could utilize 
atmospheric nitrogen. (2) The work of the writer (loc. cit.), which 
supplied the necessary link connecting these fungi directly with 
Ericaceae, and also provided additional evidence of the ability of 
certain ericaceous species to utilize atmospheric nitrogen. (3) The 
work of DuGGar and Davis,‘ who undertook a critical experimental 
review of the difficult problem of nitrogen fixation by fungi. The 
evidence provided by these workers will now be considered in his- 
torical sequence. 
(1) The researches of TERNETZ were undertaken in connection 
with an attempt to isolate the root endophytes of Ericaceae, concern- 
ing which no information was at that time available. Asa result of 
prolonged experiments, eight pycnidia-forming fungi were isolated, 
five of which were investigated for evidence of fixation of gase- 
ous nitrogen. All forms isolated were referred by Lrypau and 
Hemmincs to Phoma, and differed in the small size of the pycnidio- 
spores (4~5 yw in length) from the species previously found associated 
with Ericaceae. The five forms experimented with were isolated 
from the roots of Oxycoccus palustris, Andromeda polifolia, Vac- 
cinium Vitis-Idaea, Erica Tetralix, and E. carnea, and were named 
Phoma radiciis Oxycocct, P. radiciis Andromedae, P. radiciis Vaccint, 
P. radiciis Tetralicis, and P. radiciis Ericae, respectively. TERNETZ 
has put on record the interesting observation that these fungi, 
although isolated from plant species growing in close proximity, 
are specific strains, distinguishable by definite morphological and 
physiological characters. 
The isolation of fungal species endophytic in the roots of plants 
is a matter of notorious difficulty, and their identity can only 
be proved by formation of mycorhiza typical for the species follow- 
ing upon inoculation from pure culture into the roots of seedlings 
free from fungal infection. Those isolated by TERNETZ were 
3TerNneTz, C., Uber die oak as des atmosphirischen Stickstoffes durch, 
Pilze. Tabrb, "Wis. Bot. 44:353-408. 1 
4 Duccar, B. M., and Davis, A. ee eS in ty Ledeen of the fungi. I. 
Nitrogen ae Aa: Mo. Bot. Gand. 32413-437. 
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