CHAPTER II 



SOME CONDITIONS INFLUENCING GROWTH 

 AND DEVELOPMENT 



IT is common knowledge that a certain amount of 

 heat and an adequate supply of air and moisture are 

 essential for plant growth. All plants that have green 

 leaves require .lighten addition, to enable them to as- 

 si mi late carbon dioxid from the air, Hi^nriateit intr> its 



component parts, and elaborate th* rarhrm into SUCh 



complex substances as starch, sugar, and other carbo- 

 hydrates. 



Influence of Light on Yield. K. Pun.noul' placed 

 colored glass over different potato plants. Two plants 

 under darkened glass elaborated 3 1 and 20 grams of 

 starch respectively, while those under ordinary glass 

 elaborated 170 and 1 10 grams; at the same time plants 

 under normal conditions elaborated 223 and 361 grams. 

 To the favorable influence of abundant light this writer 

 attributes the large yield of potatoes in a season when 

 the aggregate number of hours of sunshine is unusually 

 large. At Wisconsin Experiment Station coldness and 

 cloudiness were believed to be the causes of a poor 

 yield.' 



The Amount of Moisture. The amount of 

 water the plant can obtain from the .soil is closely cor- 



K. S. R., V., p.n6. Wis. Report, 1902, p. 188. 

 8 



