56 



Influence of Sola?* Radiation on Plants. 



appeared under the red and obscured colorless glasses, and in 

 the dark. They appeared two days later under the colorless and 

 the blue, while the seeds under the obscured yellow had an un- 

 healthy look. On the 4th of May long etiolated leaflets were 

 found in the dark ; under both obscured glasses the wheat had 

 also shot up long leaves ; under the red and yellow glasses there 

 were plumes of 1 or 2 inches in length ; while under the color- 

 less and blue they only reached half an inch. The wheat-plants 

 under the colorless glass then began to grow more rapidly, and 

 soon gained the advantage of those under the blue, and still 

 more of those under the red. On the 8th they measured 3 inches, 

 while those that had grown in the dark measured 6. 



On the 12th the wheat-plants were more fully examined, and 

 drawings of them were made. It was then found that under 

 the colorless glass ten of the twelve seeds had grown. The 

 leaves were erect, of a full green color, from 4 to 5 inches in 

 height, roots long and thin, five in number, taking firm hold of 

 the brick. They had no side rootlets, but were fringed with 

 hairs. Under the blue glass, the wheat appeared like that under 

 the colorless, but smaller. Under the red, only four plants grew, 

 and they were not so regular in form, size, or general aspect as 

 those under the colorless glass. Where there was this pecu- 

 liarity, — the green stalk had been unable to burst the transparent 

 membranous sheath, and had forced itself out in a kind of loop, 

 at that part where the sheath sprung out of the seed. The roots 

 were generally flaccid. Under the yellow glass, the radicles were 

 so strong and bent so decidedly downwards, that they raised the 

 seed completely on end : they were thickly covered with hairs. 

 The stalks were short and strong, and generally bent. Under 

 the obscured colorless glass only seven seeds had germinated. 

 The leaves were of a pale green color, and had not succeeded in 

 bursting the membranous sheath ; the roots were very long. 

 Under the obscured yellow glass, the plants were of a greener 

 color than the preceding. In the dark all the plants were weak, 

 and of a very pale green color, almost yellow ; the radicles had 

 many rootlets branching out from them. 



After this, the plants under the colorless glass continued to 

 grow healthily : the hairs along the roots became very long and 

 thick, and on the 22nd of May, ramifications of the rootlets 

 began to appear. The plants under the blue did not continue so 

 healthy, nor did those under the red. Under the yellow glass, 

 both the upper plant and the roots continued to grow. Under 

 the obscured yellow glass and in the dark, the plants also con- 

 tinued growing. On the 26th, a more full examination and 

 fresh drawings were made. Under the colorless glass there were 

 ten wheat plants, generally 8 or 10 inches in height. Under 

 the blue glass there were several very thin weak plants, only 



