GRAND PERIOD OF GROWTH 



in 



of growth when grown under natural conditions ; but when 

 continuously illuminated by electric light, a method some- 

 times adopted by market gardeners to secure early crops, the 

 rate of increase falls from the first measurement of area. The 

 curves of increase in linear dimensions and in area can be 



141- 



10 

 9 



7 

 6 



5 



Jl 



UJ 



Temp. 12 75 -13 75 C 



1234 

 Time in days 



5 6 7 8 9 10 



FIG. 8. 



represented by the formula of an autocatalytic reaction.* The 

 increase in area of the total leaf surface varies with the season of 

 the year : in March and June in daylight, the rate of increase 

 is proportional to the area existing at that time, that is, the 

 growth follows a compound interest law ; but during December 

 a detrimental factor intervenes so that the rate of increase, 



* This term is explained on p. 113. 



