EXPERIMENT STATION BULLETINS. 421 



plates of agar. In most cases these females were not mature. When 

 transferred to the plates of agar, they were soon overrun with colonies 

 of bacteria and fungi, so that their development could not be followed. 

 To avoid this contamination, it Avas tried treating the female nematodes 

 as taken from the roots in various chemicals before transferring them to 

 the plates of agar. Although in some cases they remained free from con- 

 tamination after being transferred, in no case was success attained in 

 getting larvfB in this way. Either their removal from the roots or the 

 subsequent chemical treatments stopped the development of the female 

 nematodes so that they never produced mature eggs. 



The next effort was to obtain larvae by dissecting out mature or egg- 

 laying females and egg masses from the older knots on the roots of 

 various plants. Along with these females and egg masses were always 

 some larvae that had hatched out within the knots from the first eggs 

 laid by the females. Quantities of the egg masses from the root-knots 

 were treated with various strengths of chemicals and then transferred to 

 plates of agar. It was observed that the active larvae associated with 

 the Qg;g masses soon died when placed with the egg masses in the chemi- 

 cals for external disinfection. This observation caused the w^riter to 

 doubt the importance of our first theory; viz. that occasional larvae re- 

 sisted the chemical treatments applied to the soil. The more obseiwa- 

 tions that were made along this line, noting the apparent ease with 

 which the larvae succumbed to weak chemicals, the more the writer was 

 forced to the conclusion that the above mentioned theory was probably 

 not the important factor in the failure of the strong chemical, soil 

 treatments. 



Other observations made about this time appeared to give more sup- 

 port to the theory that the mature eggs Avere the resistant stage. It 

 was noted that in a few days after disinfecting mature females and egg 

 masses, active larvae began to appear on the agar plates. As it was 

 quite certain that no larvae had gone through the treatments alive, it 

 was concluded that those found on the plates were larvae that had 

 hatched from treated eggs. As a result of these observations, it was 

 decided to discontinue for the time being, the efforts to determine the 

 relative resistance of nematodes in the larval state, and to take up the 

 egg resistance theory. 



The first experiment which gave a possible explanation for the failure 

 of the field experiments was begun December 23, 1913. A large quantity 

 of mature female nematodes and egg masses was dissected from large 

 knots on Primula roots and divided into seven lots of about an equal 

 number of eggs. After being treated with the chemicals, the different 

 lots were transferred to plates of sugar beet agar. 



1. Placed the first lot in a solution made of one part of "Black Leaf 

 40" to 272 parts of water. This gave the same dilution as used in the 

 field experiments. 



2. Placed the second lot in full strength "Black T^af 40" for a few 

 minutes. 



3. Placed the third lot in 1-1000 Hg CL for a few minutes. 



4. Placed the fourth lot in 1-100 commercial 40% formaldehyde for 

 a few minutes. 



5. Placed the fifth lot in 1-10 solution of 40% formaldehyde for a 

 few minutes. 



