84 



For Baltimore the two-week cultures all show relatively 

 high values for th-^ first eight periods of the growing sea- 

 son. The seedlings of these periods were thus well along in 

 their growth at the end of t^^o weeks, and the climatic condi- 

 tions during the first half of the culture periods seem to have 

 had a relatively greater influence on the -^lants here than at 

 stations where the plants were small at the end of the two- 

 week periods. The four-week plants at this station, and the 

 four-^veek climatic averages thus correlate satisfactorily, as 

 will be evident from the following examination of the gra^^hs. 

 The graph of dry weight slopes upward with the temperature 

 index graph from the period beginning May 14 to the period be- 

 ginning June 26 and at the same time the graph of evaporation 

 is descending. For the petiod beginning June 25 good growing 

 Gonlttions ( high temperature index and low evaporation rate) 

 would seem to account for tide relatively high olant value. 

 While the sunlight conditions become less favorable from the 

 period beginning May 14 to the period beginning Jujie 25 the 

 influence of the other two climatic conditions would seem to 

 outweigh this. Prom the period beginning June 25 to the period 

 |[eginning July 23 temperature values and sunlight remain nearly 

 constant while the evaparration rate tises. The dry weight graph 

 falls as would be expected. For the period beginning Aug. 6 

 the temperature index and sunlight are at about the same values 

 as for the preceeding period, but evaporation is lower and the 

 plant graph ascends to a high value, i^rom the period beginning 

 Aug. 6 to the end of the season, the low temperature and light 

 valr.es probably account for the rapid decrease in dry weight 

 production shown in the graph representing the value of this 



