640 



SCIENCE 



[N. S. Vol. LI. No. 1330 



Eoot in Illinois. He attempted to correlate 

 the number of days with snow on the ground 

 between December and March inclusive, or 

 the niunber of days in March with freezing 

 weather while the ground was bare, or even 

 the number of days throughout the whole 

 winter when the temperature was below 20° F. 

 with the ground bare, with the yield of wheat 

 in central Illinois, and in every case, he ob- 

 tained a correlation coefficient so small as to 

 cast great doubt upon the importance of the 

 snow cover in determining the yield of wheat. 

 More si>ecifically, he found that there is 

 reason to believe that wheat has a better 

 prospect when the ground is not covered in 

 January. The best years have been those 

 with less than normal snowfall and with the 

 temperature above normal for the winter. 

 The years of poorest yield were those in 

 which the winters had heavy snow and the 

 temperatures were below normal. The com- 

 panionship of warm winters and subnormal 

 snowfall, and of cold winters and above- 

 normal snowfall, is doubtless attributable to 

 the fact that in a warm winter much of the 

 precipitation falls as rain and that a snow 

 cover tends to lower surface temperatures. 



Studies of this type are important. It is 

 true, however, that they are, through the com- 

 plexity of weather factors and the pitfalls of 

 the correlation coefficient, not always final in 

 their result. Nevertheless, each serves a use- 

 ful pui-posG in drawing the attention of agri- 

 culturists and others to the possibilities of 

 relations or aspects of a subject which are 

 either new or are opposed, as in this case, 

 by a less scientific belief. 



C. LeRoy Meisinger 



SPECIAL ARTICLES 



TRANSFERENCE OF NEMATODES (MONONCHS) 



FROM PLACE TO PLACE FOR ECONOMIC 



PURPOSES 



Speaking generally, it is now beyond ques- 

 tion that many soil-inhabiting mononchs feed 

 more particularly on other nemas. However, 

 they never follow these latter into plant roots, 

 except in the case of open root cavities fairly 

 readily accessible. They do not enter living 



plant tissues in pursuit of their prey. It 

 follows that the good they do is in devouring 

 the larvse and young of injurious nemas at 

 such times as the latter are accessible either 

 in the soil or in open cavaties in the roots of 

 plants. 



In transferring mononchs from place to 

 place with a view to making use of them in 

 combating injurious nemas, the first requisite 

 is a supply of mononchs. Such a supply may 

 be obtained from soils in which the mononchs 

 are numerous, and although we have com- 

 paratively little experience to guide us, yet 

 it is now demonstrated that supplies of 

 mononchs existing under these conditions are 

 available. Thus far these supplies have been 

 discovered more or less by accident; the cases, 

 however, are numerous enough to establish 

 the belief that special search will lead to the 

 discovery of a sufficient number of these 

 original sources of mononchs to furnish an 

 adequate supply for trial. 



The methods of collecting the mononchs, 

 and transferring them, once they have been 

 found, have been sufficiently elaborated for 

 practical purposes, and published. 



In transferring the mononchs to new situ- 

 ations, it is of course best to pay careful 

 attention to the relative physical and biolog- 

 ical conditions of the two habitats — the soil 

 from which they are transferred and that to 

 which they are transferred. The physical 

 and biological conditions of the two habitats 

 should be such as to insure the persistence of 

 the mononchs after they have been trans- 

 ferred from the old to the new habitat. If 

 the climatic and soil conditions of the new 

 habitat closely resemble those of the old 

 habitat, there is every reason to suppose that 

 the mononchs will survive and flourish if 

 there is a supply of suitable food. 



The practical details may be illustrated by 

 a hypothetical example. Suppose a region in 

 Holland having a sandy soil has distributed 

 in it as a plant pest the devastating nema, 

 Tylenchus dipsaci, which, though more or less 

 prevalent, is not doing very serious damage 

 because held in check by mononchs. Suppose 

 the existence of another region, like that in 



