434 STATE BOARD OF AGRICULTURE. 



This steam experiment was next repeated on an adjoining plot of soil 

 exactly as before, except that tlie steam at eighty pounds pressure was 

 run into the pan lor lilteen minutes instead of thirty minutes. At the 

 end of the period the pan was removed and the potatoes were dug. The 

 I)otato at three inches below the surface was thoroughly cooked. Pota- 

 toes at six aud twelve inches below the surface were partly cooked. The 

 potato at eighteen inches below the surface was very hot. Of these two 

 treatments, the thirty minute steaming was the better, as judged by the 

 condition of the potatoes. Where the potatoes were well cooked, it is 

 quite reasonable to suppose that the nematodes were killed, but the 

 writer is not certain of this point.* 



ACKNOWLEDGMENTS. 



The writer is indebted to Dr. E. A. Bessey, Botanist, Michigan Agri- 

 cultural Experiment Station, for many suggestions and much helpful 

 advice. 



To Dr. L. E. Jones, Plant Pathologist, Wisconsin Agricultural Experi- 

 ment Station, the writer is indebted for much helpful criticism. 



LITERATURE. 



The literature cited here is chiefly that which has a bearing on this 

 particular problem. For the more general literature on the subject, see 

 the bibliography by Bessey (2). 



Atkinson, George F. . 



(1) A preliminary report upon the life history and metamorphoses 

 of a root-gall nematode. Heterodera radicicola (Greef) Muhl., 

 and the injuries caused by it upon the roots of various plants. 

 Alamaba Polytechic Institute Bui. N. S., No. 9, 1889. 



Bessey, Ernst A. 



(2) Boot-knot and its control. Bureau of Plant Industry Bui. 

 217:7-81. 1911. 



Cobb, N. A. 



(3) Koot-gall. The Agricultural Gazette of New South Wales. Vol. 

 12, No. 9, pp. 1041-1052. 1901. 



(4) The internal structure of the gall-worm. The Agricultural Ga- 

 zette of New South Wales, Sidney, Vol. 13, No. 10, pp. 1031-1033. 

 1902. 



Rolfs, P. H. 



(5) Tomato diseases. Florida Agricultural Experiment Station, 

 Bui. 91; pp. 15-34. 1907. 



Stone, George E. and Smith, Ealph E. 



(6) Nematode worms. Hatch Experiment Station of the Mass- 

 achusetts Agricultural College, Bui. 55; pp. 2-67. 1898. 



♦Note : Observations made by E. A. Bessey in the summer of 1915 on these and similarly 

 treated adjacent lots of formerly badly infected soil show the total absence of root-knot 

 nematodes both one and two years after the steam treatment. 



