SOIL STERILIZATION 89 
Steam Sterilization 
Temperature required.—Definite information gained 
from experiments relating to this question is contained in 
Bulletin 55 of the Massachusetts station, from which is 
quoted the following: 
“Our experiments upon this point were numerous, and they were 
made with earth containing abundance of nematodes of various 
species in all stages of development. For the sake of convenience 
we will designate these experiments as a, b, c, etc. In all of these 
experiments we employed cucumbers in pots of various sizes (from 
4 inches to 10 inches), and the plants were left until they were 
sufficiently large to show root galls upon them if nematodes were 
present in the soil, In every case except ‘a’ the pots containing the 
infested earth were sterilized in an Arnold steam sterilizer, and 
when moderate heating was required they remained in the sterilizer 
only a few minutes. 
“The earth in experiment ‘a’ was part of a large lot which was 
sterilized in a box by means of steam from a boiler. In every in- 
stance numerous microscopic examinations were made of the soil 
and roots of the plant in order to determine whether nematodes 
were present. The non-parasitic species are generally present in al- 
most every soil, and their presence can very often be suspected by 
the coloration of the root. They are generally found on the older 
parts of the root near the surface of the soil, as indicated by the 
dirty brown color of the epidermal tissue. The experiments are as 
follows: 
“Exp. a. Six 4-inch pots were filled with infested earth which had 
been heated to 212 degrees. The pots were also sterilized and the 
cucumber seeds after soaking 12 hours in water were placed for 
10 minutes in a saturated solution of corrosive sublimate, and be- 
fore using were rinsed with sterilized water. During germination 
and the growth of the plants they were always watered with filtered 
water. Hence all source of contamination was eliminated. Results, 
no nematodes. 
“Exp. b. Six plants treated as above. Result, no nematodes. 
“Exp. c. Twelve pots of cucumbers, the seeds of which were 
treated as in Exp. ‘a’ and the plants watered with sterilized water. 
