234 



raise plants peculiarly fitted for wet climates or for cold climates, 

 we begin with the seed that was rij^ened in wet or cold seasons. 



I think that probably a further prosecution of Linsser's studies 

 would have led to the conclusion that the influence of sunlight and dif- 

 fuse sky light is the next important factor in vegetation, and that the 

 quantity and quality of the seeds produced — that is to say, of the crop 

 as distinguished from the mere epoch of ripening — depends upon the 

 ratio of the nutrition carried up in the sap to the total intensity of 

 sunshine. The grain harvests of the world may be divided into 

 zones «, Z>, (?, analogous to the phenological zones that Linsser has 

 given, and in which the quantity of the harvests is large when the 

 nutrition is sufficient to use up all the sunshine, but is small when 

 either nutrition or sunshine is deficient. As the plant begins a new 

 cycle so soon as the last is finished and usually is delayed by the 

 speedj'^ approach of winter cold or autumnal drought, therefore 

 Linsser's laws would lead us to the conviction that by artificially 

 regulating the temperature, moisture, sunshine, or artificial light, and 

 the nutrition in the soil, we ought to be able to develop an ideal 

 method of cultivation that should gi*eatly increase the number of 

 crops per j^ear and the yield per acre, and especially so within small, 

 limited areas that are protected by cover from injurious frosts. 



The need of water for the varieties of plants and seeds usually cul- 

 tivated has led to great engineering projects for irrigation, and the 

 scarcity of natural rainfall has led to wholesale condemnation of 

 many arid regions as being unfit for profitable agriculture, but the 

 progress of knowledge now shows us that nature has a power at work 

 gradually overcoming these disadvantages, and that man by taking 

 advantage of her ways may profitably cultivate crops in extreme cli- 

 mates and soils, not so much by irrigation as by developing seeds and 

 plants that suit the natural circumstances, just as our own ancestors 

 developed our European grains from the grasses of Asia or our wide- 

 spread maize from the weeds of Mexico. It is the duty of our agri- 

 cultural experiment stations to lead the way in this evolution of new 

 varieties quite as much as in the mere introduction or acclimatization 

 and study of old varieties. Now that we have learned the secrets of 

 Nature's method of evolution we must hasten to apply it to the needs 

 of mankind. 



DOVE. 



In 184G H. W. Dove wrote as follows : 



In the tropical regions the mean temperature of an}^ year differs 

 but little from that of any other, but the quantity of rainfall differs 

 largely. The result is that the yield of crops varies exceedingly, not 

 onh^ on loAvlands that depend upon the periodical floods of the rivers, 

 but also on the islands, where there are no large rivers. Therefore 

 in these climates the agriculturist cares less about the temperature 

 than about the rainfall. 



