154 BOTANICAL GAZETTE [august 



open ground up to the brim. A bell jar of about the same diameter as 

 the pots was covered with brown paper and was placed over one of the 

 pots for a certain time during the morning and over another during the 

 afternoon, the exact duration of shading being noted in each case. 

 The other two pots were left as checks. Care was taken to place the 

 bell jar over the plants as far as possible during the time when no rain 

 was falling, as the presence of additional moisture in some of the pots 

 would have caused a disturbing factor in estimating the results. The 

 temperature inside the bell jar was not noted, but there is no reason to 

 believe that it was so different as to have any marked effect. 



The pots were labeled A, B, C, and D; of these A and C were shaded, 

 while B and D were the check pots. The seeds were sown in the pots on 

 June 13, 191 6. On June 26, when the first leaf in succession to the 

 cotyledons had developed, 80 seedlings were left in each pot; the others 

 in excess of this number were pulled up and thrown aw r ay. 



Pots A and C were shaded on 1 1 days, beginning with June 26 and 

 ending with July 10, the total duration of darkening being 28 hours and 

 23 minutes, in the case of pot A; and 28 hours and 28 minutes in pot C, 

 A being shaded before midday and C in the afternoon. 



On July n the number of plants in each pot was 64 in A, 68 in B, 

 78 in C, and 63 in D. On this date five of the tallest plants in each 

 pot were pulled up, measured, and weighed, after shaking the earth from 

 the roots. The average length and weight per plant in each lot were as 

 follows: 



Pot Length Weight 



A (darkened) 109 . 2 mm. 122 mg. 



B 112. 4 125 



C (darkened) 111.2 



121 



D 



12=:. 8 212 



From July 12 to 20 inclusive, pots A and C were again shaded daily, 

 except on the 16th, and the total period of darkening was 17 hours and 

 1 minute. On July 22 the 10 tallest plants were selected from each pot, 

 measured, and weighed, with the following results per plant: 



Pot Length Weight 



- 



A (darkened) 206 . 5 mm. 478 mg. 



B 



238.2 572 



C (darkened) 183 . 5 430 



D 256.5 936 



On July 31 the first flowers were opening in pots B and D, while the 

 first flower opened in pot A on August 2, and in pot C on August 4- 





