March 25, 1921] 



SCIENCE 



277 



illuminatioii. Indeed it may be hazarded that 

 it is this stimulus which normally controls 

 all recurrent periodic phenomena in plants 

 and animals. Just how it is to be correlated 

 with certain other phenomena which form the 

 basis of Kleb's salts-carbohydrate theory is not 

 yet clear. It is quite possible that entirely 

 different stimuli affect the control of vege- 

 tative and reproductive phenomena so as to 

 give similar end reactions. The Garner- 

 Allard factor certainly provides a new method 

 of approach to study the internal factors that 

 control the plant's activities. It is probably 

 not a wild guess that these internal factors 

 are as numerous as the genetic factors con- 

 cerned in the plant's heredity mechanism. As 

 it happens, the approach to this problem and 

 the progress made in its solution was purely 

 from the agi'onomic viewpoint and with the 

 object of solving an agronomic puzzle. This 

 is worthy of mention as an illustration of the 

 fact that the plant culturist gets a different 

 contract with plant phenomena from the 

 botanist of the laboratory. 



The plant culturist has long been familiar 

 with the phenomena illuminated by Garner 

 and Allard. It is this factor which in the 

 case of field crops led to date of seeding trials 

 — by which in a purely empirical way the best 

 date of seeding or planting for each locality 

 was determined. Any one who has seen plots 

 of millet, for example, planted at succeeding 

 dates will appreciate how much this factor 

 alone can affect yields. 



Another important factor affecting yield is 

 the spacing of the plants whether secured by 

 rate of seeding or by planting at measured 

 distances. It is easy to understand why too 

 sparse seeding will reduce yields and also to 

 comprehend that crowding may result un- 

 favorably — but it is doubtful if any other 

 method than actual trials will ever enable us 

 to ascertain the optimum rate of spacing for 

 any particular crop at any specific place. 

 Curiously enough as Mooers has shown, 

 varieties of maize not markedly unlike have 

 very different optima as regards spacing. 

 In southern India where rice culture is very 

 ancient, and the seedlings are transplanted by 



hand, Wood was able to increase yields 

 materially by determining the optimum 

 spacing- distance. Incidentally this greatly 

 reduced the amount of seed necessary which 

 in a country where the daily wage is eight 

 cents was a considerable economic factor. 

 Such empirical data as these are highly im- 

 portant in plant culture — and it seems not 

 unlikely that they always will have to be 

 determined by test and not by some mathe- 

 matical equation. 



In America, crops are mostly planted as 

 pure culture, in India usually as mixed cul- 

 tures, one of the plants commonly a legume. 

 Mixed cultures usually outyield pure cultures 

 — but except where the crops are garnered by 

 hand, the increased cost of harvesting becomes 

 an important economic factor. Why mixed 

 cultures, even of the small grains, outyield 

 pure cultures is an interesting phenomenon, 

 and one can easily theorize to his heart's con- 

 tent. In nature plants are usually, but not 

 always, in mixed cultures. Actually we know 

 practically nothing of these phenomena except 

 the observed or experimental facts. 



Perhaps no one will contend that a gradu- 

 ate of the best botanical courses in America 

 is thereby fitted to undertake the cultivation 

 of any crop, let alone such as require special 

 knowledge and skill. It is remarkable to how 

 great a degree that success in growing a crop 

 is based on the slowly accumulated results of 

 experience. During the war you will remem- 

 ber there was urgent need for a large supply 

 of castor beans. It is doubtful if in the whole 

 history of American agriculture there was 

 ever a more dismal failure than the attempt 

 to produce these beans. There was an abun- 

 dance of theoretical data based on the culture 

 in other countries, but in attempting to grow 

 the crop in the United States the handicaps 

 of unadapted varieties and unexpected diffi- 

 culties proved disastrous. Perhaps in no other 

 industry is the advice " Make haste slowly " 

 more applicable than in agriculture. 



I have endeavored to point out by a few ex- 

 amples of plant cultural problems how dif- 

 ferent they are from those considered in the 

 conventional botany of the schools. The 



