268 



SCIENCE 



[N. S. Vol. XXXVIII. No. 973 



process could only result in a continuous 

 freeing of fertility. These authors have 

 also apparently made the mistake of study- 

 ing some other soil than the one which 

 should be studied. All of the phenomena 

 which they mention for sewage-sick soil 

 can in all probability be explained on nor- 

 mal chemical, physical and biological 

 grounds without the necessity of intro- 

 ducing a reversed Metchnikoff theory. 



It will be noted that all these theories 

 have a strong chemical bearing, that, in 

 fact, all are trying to explain crop de- 

 terioration on the basis of chemical deple- 

 tion or modification of the soil. They, ap- 

 parently, all ask: "What is the matter 

 with this soil?" rather than, "What is the 

 matter with the crop 1 ' ' They do not allow 

 the cropping plant much character of its 

 own as to ability to feed itself when fer- 

 tility is available; and, to my thinking, 

 there is a stumbling block in the way of aU 

 these theories. None of them explain im- 

 mediate crop failure or modification on 

 virgin lands, nor do they explain the pro- 

 duction of seed of deteriorated quality on 

 old-worked lands of high available fertility. 



As to explaining the types of seed deteri- 

 oration which the millers have under dis- 

 cussion, I am convinced all fail. Our ex- 

 periments teach that there are other inter- 

 fering causes than lack of fertility or of 

 the presence or absence of toxines in the 

 soil, or the presence or absence of a par- 

 ticularly good bacterial flora, or the pres- 

 ence ox absence of amoeboid organisms 

 which feed upon them. For example, in 

 the case of fruit culture, vegetable garden- 

 ing and potato culture, I would call atten- 

 tion to the fact that sanitation applied to 

 cropping methods has made a record which 

 should long ago have aroused the chemists 

 and the teachers of agriculture from their 

 apathy with regard to the influence of in- 

 terfering diseases upon cereal cropping. 



I recognize that soil fertility in chemical 

 matter, taken with climate and variety, 

 constitute the primary gage of the crop- 

 producing power of a soil, but I also feel 

 sure that I am pointing out the chief in- 

 terfering factor which accounts for the 

 irregularities in cereal crop production, 

 namely, infections disease resident in the 

 seed and in the soil. My experience with, 

 observation on, and experiments upon 

 potato-sick soil, flax-sick soil, wheat-sick 

 and oat-sick soils leave me no room to 

 doubt that the various chemical theories of 

 soil deterioration or depletion do not in 

 any way explain the causes of deteriorated 

 grain as seen under the one-cropping sys- 

 tem on soils which are characteristically 

 cereal lands. Soil fertility is primary, but 

 a disease problem is superimposed. 



Root diseases of cereals, as in the ease of 

 potatoes, in all probability account for 

 many of the confusing results which have 

 been obtained under the best and most 

 persistently conducted series of crop rota- 

 tion, soil fertilization, water culture experi- 

 ments, etc. These experimenters never 

 used, with certainty, healthy seedlings. 

 When they used manure, they sometimes 

 did and sometimes did not introduce crop- 

 destroying diseases. When they have used 

 artificial fertilizers they sometimes did and 

 sometimes did not apply them to the crops 

 which were particularly subject to disease. 

 So, also, in the past conducting of variety 

 tests of cereal grains, the results are very 

 largely vitiated. In the presence of dis- 

 ease, a resistant variety has been given 

 undue credit for yield and quality, while a 

 non-resistant variety has been unjustly 

 militated against. 



My experience with cereal crops with 

 reference to the application of fertilizers, 

 the trial of varieties, experiments in seed 

 selection, seed breeding and seed treatment, 

 and seed purification furnish data which 



