AMERICAN 
JOURNAL OF BOTANY 
Vol. IV November, 1917 No. 9 
EFFECT OF SOIL TEMPERATURE ON THE GROWTH OF 
BEAN PLANTS AND ON THEIR SUSCEPTI- 
BILITY TO A ROOT PARASITE 
Donald Reddick 
The general opinion prevails that temperature plays an important 
r61e in the infection of a host by a fungous parasite. The experi- 
mental data showing just what this role is, however, are very meager. 
In the case of infection of aerial parts other factors are interrelated 
with temperature, such as persistence of moisture for spore germina- 
tion, rapidity of germination of spores, and so forth, but in the case 
of infection of roots by organisms persisting in the soil these conditions 
ordinarily do not enter. Apparently the soil-inhabiting parasites are 
largely capable of saprophytic existence so that, given the requisite 
amount of soil moisture to maintain plant development, the parasite 
is able to grow and reach the roots of a susceptible host. Oilman^ has 
recorded observations on the relation of infection by Fusarium con- 
glutinans Wr. on cabbage to soil temperature conditions and thinks a 
high soil temperature favorable to infection. Oilman^ continued this 
work with F. conglutinans and appears to have established the point 
just mentioned, although the control of conditions in some of his ex- 
periments was not all that might be wished for. Tisdale^ arrives at 
similar conclusions in connection with the infection of flax (Linum 
usitatissimum) by Fusarium Lini Bolley and states that the low critical 
temperature is about i5°-i6° C. 
^ Gilman, J. C. The relation of temperature to the infection of cabbage by 
Fusarium conglutinans Wollenw. (Abstract.) Phytopathology 4: 404. 19 14. 
Cabbage yellows and the relation of temperature to its occurrence. Ann. Mo. 
Bot. Gard. 3: 25-82. 1916. 
2 Tisdale, W. H. Relation of temperature to the growth and infecting power 
oi Fusarium Lini. Phytopathology 7: 356-360. 191 7. 
[The Journal for October (4: 439-512) was issued October 2, 1917.] 
513 
U NOV 30 1917 
