Influence of Sola?- Radiation on Plants. 57 



about 2 inches high. Under the red, the development was but 

 an inch and a half, in the case of three plants. The rest that 

 were growing had not succeeded in breaking the membranous 

 sheath, but were contorted in their efforts to escape. Under the 

 yellow, three plants had grown like those under the colorless 

 glass ; three others were not so fully developed, while the re- 

 maining four had not germinated. Under the obscured colorless 

 glass, the wheat had not grown since May 12th. Under the 

 obscured yellow, I found six plants. In the dark, the plants had 

 grown much as under the obscured yellow glass, but they were 

 still longer, weaker, and paler in color. 



On J une 5th, the experiments were stopped. The plants under 

 the colorless glass were healthy in every respect, and were of a 

 better green than any of the others. Under the red glass, one 

 of the plants was found to have shot up several small leaflets 

 outside the transparent sheath, which it had been unable to 

 pierce. 



The following table shows the number of seeds of wheat 

 which had put forth roots, and the average length of the princi- 

 pal roots ; and also the number of seeds from which plants had 

 grown, together with the average length of the principal leaves. 





Roots. 



Le 



aves. 





No. of plants. 



Length. 



No. of plants. 



Length. 





10 



2'5 inches 



10 



10 inches 



Blue, 



6 



0-75 " 



6 



4 " 



Red, 



8 



35 



4 



4 " 





7 



2 



6 



9 " 





6 



35 



3 



2 " 





is 



0-75 " l 

 2-5 " } 



7 



8 " 



Dark, 



7 



3 



6 



13 " 



The plants were removed from the bricks, spread out on the 

 table, and allowed to dry in the air for eighteen hours. The 

 following table shows the weight of those which had grown 

 under each of the various conditions of light. The original 

 weight of the twelve corn-seeds was in each instance 8 grains, 

 giving as the average weight of each seed 0*66 grs. 





No. of plants 

 which had 

 germinated. 



Weight. 



Average weight 

 of each. 



Average in- 

 crease upon 

 original weight. 





10 



31 grs. 



3-1 grs. 



2 4 grs. 



Blue, 



6 



4 " 



066 " 



0 " 



Red, 



8 



4-5 " 



056 " 



—01 " 



Yellow, 



7 



8 " 



11 « 



0-4 " 





6 



4 " 



0-66 " 



0 " 





7 



10 " 



1-4 " 



0-7 " 



Dark, 



7 



9 " 



1-3 " 



0-6 " 



The increase in weight of the plants which had grown under 

 the colorless, the dark, and the yellow glasses, was due, of course, 



SECOND SERIES, VOL. XXII, NO. 64. JULY, 1856. 8 



