Influence of Solar Radiation on Plants. 



55 



The first series of experiments was made in common air, under 

 the seven various influences of colored light and obscurity, which 

 have been described in treating of the hyacinths. The colored 

 shades were arranged before the windows, as described above, 

 and they dipped into plates of water, so that throughout the ex- 

 periments they were filled with an unchanged atmosphere, satu- 

 rated with moisture. Twelve grains of wheat and twelve peas 

 were taken for each separate experiment, and their weight was 

 noted while they were still dry. They were placed on bricks 

 within the glass shades, the bricks standing in the water, so that 

 they were always damp. Another arrangement was made, simi- 

 lar to that just described in every particular, except that the 

 seeds were in the open air of the room, without any cover. 



The experiments were commenced on April 21st. The fol- 

 lowing is a table of the weather, and of the temperature taken 

 in the shade at mid-day during the time that the various experi- 

 ments with peas and wheat continued : — 



April 22. 

 " 23. 



cloudy 





May 



15. 



fine 



69° 







« 



16. 



variable 



65 



" 24. 



do! 







17. 



fine 



66 



" 25. 



variable 







18. 



cloudy and wet 



64 



" 26. 



do. 



60° 





19. 



fine 



66 



" 27. 



wet 



57 





20. 



do. 



67 



" 28. 



variable 



56 





21. 







" 29. 



do. 



56 



u 



22. 



cloudy and wet 



64 



" 30. 







« 



23. 



fine 



65 



May 1. 



2. 



wet 



55 





24. 



variable 



63 



variable 



55 





25. 



fine 



66 



3. 



do. 



59 





26. 



do. 



67 



" 4. 



fine 



61 



« 



27. 



wet 



63 



5. 



variable 



63 



u 



28. 







6. 



cloudy 



60 



<« 



29. 



wet 



63 



" 7. 





56 



M 



30. 



do. 



63 



8. 



variable 







31. 



fine, but cloudy 



65 



9. 



wet 



60 



June 



1. 



fine 



66 



" 10. 



fine 



58 





2. 



wet 



63 



" 11. 



cloudy 



62 





3. 



fine 



65 



" 12. 



fine 



60 





4. 







" 13. 



cloudy 



64 





5. 



cloudy 



63 



" 14. 





65 





6. 





63 



"We shall first consider the growth of the wheat ; afterwards 

 that of the peas ; and then compare the two. 



On April 26th the corn seeds were found just beginning to 

 burst under all the seven glasses, those under the obscured 

 yellow being the most advanced. Further growth was visible 

 the following day under that glass, and also under the obscured 

 colorless, and the yellow, though the plume did not appear in 

 any case till the 29th. On May 1st the radicles under the color- 

 less and blue glasses were of considerable length, but those 

 under the obscured colorless and the red were longer, while the 

 longest were under the yellow glass. On April 29th plumes 



