10 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 97 



Experiment 8. — In the last experiment of this series, the same types 

 of lamps were used. Also each culture contained three tomato plants. 

 The first four cultures (nos. i, 2, 3, 4) were arranged around the 

 mercury lamp at approximately equal distances. The other two (nos. 

 5 and 6), together with those numbered 3 and 4, were located about 

 equal distances from the water-cooled 115-watt Mazda projection 

 lamp. The intensity measurements taken at the beginning of the 

 experiment are shown in table 10. 



Table 10. — Radiation measurements in experiment 8 



Intensity measurements 



Culture 



Watts/cm^ Foot-candles 



no. Mazda Hg Total Mazda Hg Total 



1 0071 .0048 .0119 350 700 1,050 



2 0071 .0047 .0118 350 700 1,050 



3 0140 .0046 .0186 800 700 1,500 



4 0144 .0045 .0189 800 700 1,500 



5 0137 .0010 .0147 900 200 1,100 



6 0146 .0010 " .0156 900 200 1,100 



At the end of three weeks the plants were photographed and har- 

 vested. Since each culture of three plants was duplicated, the average 

 of the six plants is shown in table 11. 



Plants of cultures 3-4 were best in general appearance and had the 

 thickest stems. Those of cultures 5-6 were lightest green. Plants 

 with longest roots were found in cultures 5-6; those with shortest 

 roots occurred in cultures 1-2. 



The general appearance of the cultures about the two lamps in this 

 experiment may be seen in plate 3, and the appearance of the tops 

 and roots of the plants at the end of the experiment is seen in plate 4. 



It will be recalled that in experiment 6 the ratio of dry weight to 

 total energy increased with the percentage of added radiation from 

 the mercury lamp. Also in experiment 7, table 9, the three cultures 



