82 



of a large decrease in the temperature index value but the 

 high value of sunshine intensity during the last two weeks 

 of the period may account for this behavior of the plant. 

 The l^t two four-week periods of the season are characterized 

 by low light and temperature index values throughout, which may 

 accotmt for the low plant values shown oj these neriods. 



For College, the four-week climatic values do not seem 

 to account for the lov; growth rate for the period beginning 

 June 19 nor for the extremely high growth rntes for the periods 

 beginning July 17 and July 31 respectively. The first-men- 

 tioned r)eriod would seem to have good growing conditions fhigh 

 temperatue index value and low evaporation rate while the last 

 two have about the same temperature as the first with high 

 evaporation rates). Here the climatic conditions during the 

 seconi two weeks of growth do nOt seem to give any suggestion 

 as to why the culture started June 19 should show such a lo-^ 

 rate of growth in comparison with the cultures started July 17 

 and July 7>1, Several noints worth calling attention to come 

 out of a comparison of the two and four-week graphs for the 

 cultures started July 3, July 17 md July 31. It will be 

 noted that the two-week culture started July 3 is relatively 

 high in leaf -product (which is proportional to dry \-eight) 

 but that after four weeks of growth these same plants shov a 

 relatively low dry weight. An explanation for this is sug- 

 gested by the sharp rise in evaporation rate from the first 

 to the second two weeks of this culture oeriod, /'periods be- 

 ginning July 3 and July 17 on *"he two-week g:^aph1. Also, for 

 the series of two-week culturs, +:he one started -Tuly 17 shears 

 the highest leaf product for the season at this station, but 



