Feb., 1923] CLAYTON — TEMPERATURE AND FUSARIUM WILT 87 
5. Gray, J. A study of the non-parasitic leaf spot of tobacco. M. S. thesis deposited 
in the library of the University of Wisconsin. 1920. 
6. Haskell, R. J. Fusarium wilt of potato in the Hudson River Valley, N. Y. Phyto¬ 
path. 9: 223-260. 1919. 
7. Humphrey, H. B. Studies on the relation of certain species of Fusaria to the tomato 
blight of the Pacific Northwest. Wash. Agr. Exp. Sta. Bull. 115: 22. 1914. 
8. Livingston, B. E. Drying and wilting of plants. Johns Hopkins Univ. Circ. 36: 178. 
I9I 7 - 
9. Rogers, S. The culture of tomatoes in California, with special reference to their 
diseases. Cal. Agr. Exp. Sta. Bull. 239. 1913. 
10. Rumbold, Caroline. Pathological anatomy of injected trunks of chestnut trees. Proc. 
Amer. Physiol. Soc. 55; 485-492. 1916. 
11. -. The effect on chestnuts of substances injected into their trunks. Amer. Jour. 
Bot. 7: 45-56. 1920. 
12. Sherbakoff, C. D. Fusaria of potatoes. Cornell Univ. Agr. Exp. Sta. Mem. 6. 1915. 
EXPLANATION OF PLATES 
Plate VIII 
Petri-dish cultures of Fusarium lycopersici prepared by inoculating the center of each 
plate of potato agar with a single drop of a spore suspension of the organism. These were 
incubated for five days at a graduated series of temperatures ranging, as indicated, from 
8° to 38° C. The highest temperature at which the fungus can develop, i.e., the maximum 
temperature, lies between 35 0 and 38° C., the optimum for its growth is about 28° C., 
and the minimum between 8° and io° C. 
Plate IX 
A. A plant inoculated and held at a warm temperature, favorable for the wilt (25°- 
30° C.), until the disease was well advanced, and then moved into a cool temperature 
(i5°-20° C.) where the disease was checked. The stem on the right is the old main stem, 
all the leaves and the growing tip ( x ) having been killed by the wilt while the plant was 
still at the warm temperature; the growing tip, now dead and dry, may still be seen attached 
to this stem. The new growth, consisting of one shoot at the base of the stem and one 
higher up, was all formed after the plant had been exposed to the cool temperature. This 
new growth appeared perfectly healthy in every respect. 
B. Representative plants taken from the temperature tanks in soil-temperature 
Experiment III. Note the prevalence of wilted plants between 22 0 and 31 0 C. and the 
healthy ones which grew at lower and higher temperatures. The optimum soil temperatures 
for the development of the disease, 28° and 31 0 C., stand out very conspicuously here. 
C. Tops cut from control plants of the same experiment. They illustrate the vegeta¬ 
tive development of uninoculated plants grown in sterilized uninoculated soil. 
A comparison of photographs B and C shows the close correlation between the optimum 
temperature for the vegetative growth of the plant (22 0 to 31 0 C.) and the most pronounced 
development of the disease. Note also by comparison with Plate VIII that the .same favor¬ 
able temperatures hold for the development of the parasite. 
Plate X 
Representative plants grown in inoculated soil for 20 days in the temperature tanks 
of soil-temperature Experiment III. These plants were grown under exactly the same 
conditions with the exception of the soil temperatures, which were held at 23 °, 28°, 31 °, 
and 33 0 C. respectively. These, plants show more clearly tfian those in Plate IX, B, the 
stunted and wilted condition of the stems and foliage at 28° and 31 0 C. This is in sharp 
contrast to the absence of any signs of the disease at either the lower temperature (23°) 
or the higher (33°). 
