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JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



seedling or initial stage as well as in the adult condition, twelve- 

 young plants were selected, as nearly the same size and stage of 

 growth as possible as those used in the experiments. They were 

 weighed fresh, and again when perfectly dried. The average 

 amount of dry substance thus obtained (viz. 2*G grammes in a 

 total weight of 27*15 grammes) was reduced to a standard of 

 10 grammes, of which the water constituted 9, and the dry sub- 

 stance 1 gramme.* This afforded a basis for calculating the dry 

 substance in the experimental plants, first in their initial stage 

 {i.e. 10 grammes), and secondly in their adult or final stage, when 

 taken up on June 30. 



On the other hand, the dry substance in the three plants 

 grown in the frame without any glass, but freely exposed, supplied 

 another basis for the final comparison. 



Assuming the dry substance of these latter plants to be the 

 normal amount acquired by assimilation, the differences in the 

 amounts of dry substance of those grown under coloured or clear 

 glass would, therefore, indicate the degrees of disadvantage in 

 growing the Lettuces under them respectively. 



Table I. (Total Weights). 



Col. 1 gives the mean, final or total weights calculated from 

 an assumed initial weight of 10 grammes for each plant.t 



Col. 2. This represents the total increase or gain above the 

 original 10 grammes. 



Col. 3 represents the increase per cent. 



Mean temp. (I) (2") (X\ 



Pi 70° 26*8 10-3 263 



Y 73° 43-5 33-5 48$ 



G (52° 15-7 5-7 157. 



B G4° 249 14-9 249 



CI 05° 44-7 34-7 447 



Open 03° 07 3 57-3 (373 



Table II. (Dry Substance). 



Col. 1. The calculated total amounts of dry substance ob- 

 tained by assimilation. The amount in the assumed original 

 weight of 10 grammes was 1 gramme, or 10 per cent. 



* More accurately "9G7 gr., but 1 gr. is quite accurate enough to show 

 comparative results. 



t Thus, e.g., the mean weight of the three seedlings under red glas3 

 was originally 7*08 grs. ; that of their total weights was finally lS-.V.i grs. ; 

 hence. 1 B'«9 x 10 : 7*00 2C'S, or the final mean, or total \ve:ght by 

 calculation. 



