M. Camille Flammarion has made many interesting experiments on the growth of plants under different coloured rays. In one experiment he took young lettuces from the same plot of ground, and all the same size. His results showed that—
| Under | red glass | lettuce | grows four times as quickly as in direct sunlight. |
| ” | green | ” | ” slightly quicker than in sunlight. |
| ” | blue | ” | becomes very stunted. |
In another experiment he worked with Indian corn.
| In sunlight | one | plant | grew to | 25 | inches. | |
| Under | red glass | ” | ” | ” | 18 | ” |
| ” | green | ” | ” | ” | 8 | ” |
| ” | blue | ” | ” | ” | 6 | ” |
| Beans | flourished | under | white | and | red | glass. |
| ” | perished | ” | green | ” | blue | ” |
From the above it seems that blue glass is bad for plants; but this is not always so, as is seen from the experiments of General Pleasanton, where he grew the best grapes in his district by using alternate white and blue glass in his greenhouses. Babbit states that blue light develops germination of plants, while red and yellow develop animalculæ. Yellow rays cause carbon to deposit from the air, and so form the woody fibre of plants. Red and yellow cause seeding and fruitage.
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