6 The Bulletin. 



The environmental conditions of plant life have generally been de- 

 fined as climatic, geographical and physiographical location, and con- 

 ditions of food supply. 



Climate has hiiJierto been stressed more than any other factor in 

 plant production. And while no one will assert that climate is not the 

 controlling factor in the latitudinal and altitudinal distribution of 

 plants, yet, in the same latitude, where climate is uniform, except over 

 small areas of different elevation, this factor can not be said to account 

 for the wide differences observed in the character and development of 

 the different varieties of the same species of plant; and while we would 

 not care to minimize the very important place occupied by climate in the 

 production of crops, still, snice this factor has been so generally empha- 

 sized by leading scientists and experimenters in the field of agriculture, 

 we may be excused for calling attention more particularly in this paper 

 to the influence exerted by the type of soil in which the plant is forced 

 to grow. The soil has, indeed, always received a passing consideration 

 as a factor associated with the food supply of plants, but we hope to 

 show in the following pages that soil, or soil type, plays a vastly more 

 important part in plant production than has hitherto been accorded it. 



ADAPTATIONS GENERALLY RECOGNIZED. 



When the plant is confined in a new environment it either dies or so 

 readjusts its physical structure as to become gradually adapted to the 

 new conditions surrounding it. The plant organism responds to every 

 touch of environment. 



There are certain broad adaptations of plants to soil environments 

 that are recognized by every man possessed of a fair knowledge of 

 agronomy. In the great wheat and corn sections of the central west a 

 heavy clayey loam, occurring in what is technically known as the Miami 

 series of soil, is admitted to be best suited to the former, while a silty 

 loam, belonging to the Marshall series, is best adapted to the latter 

 cereal. For early truck any experienced gardener will select a light 

 sandy soil for outdoor culture. Every experienced grower knows that 

 the alfalfa plant, regardless of climate, requires a large percentage of 

 lime in the soil — a calcareous soil — to make its best yield. 



ISTot only do the above named conspicuous and rather well defined 

 adaptations of plants to peculiar soil environments exist, but on close ex- 

 amination we shall find that plants have adapted themselves to every 

 physical environment in which it is possible for them to exist, or, as 

 Bailey has put it, "Every physical environment produces adaptive 

 changes in plants." 



This theory of adaptation of the plant to the environment has engaged 

 the serious thought not only of leading agriculturists but of leading 

 biologists as well, and the only defense of this paper is that too little 

 attention has been given the part played by the soil type per se in the 

 many observed adaptations. This thought could hardly have been 

 more strongly or fittingly expressed than by Hilgard when he said: 

 "Under given climatic conditions every distinct soil type bears a charac- 

 teristic vegetation." He further states that the natural vegetation of 

 any area represents the best adaptation of plants to soils in the results 



