[105]

George

Geranium Ibericum cosine of 27°

Linum Berendieri — — of 33°

p. 410-411

27° Exposes .891 of its area = lessen radiation 11 percent

33° -- .839 --- 16 per cent

On the other hand when we get down to low angles such as 30° about 30° the saving of radiation is as nothng. For instance

State of torsion, & as soon as light diminishes & no sun to keep light [illeg] & rises

[Movement in plants, p. 298: "On the other hand, when the angular rise of cotyledons or of leaves is small, such as less than 30°, the diminution of radiation is so slight that it probably is of no significance to the plant in relation to radiation. For instance, the cotyledons of Geranium Ibericum rose at night to 27° above the horizon, and this would lessen radiation by only 11 per cent.: those of Linum Berendieri rose to 33°, and this would lessen radiation by 16 per cent."]

[105v]

[diagram] When a leaf is inclined at 60° above Horizon, the radiation from its surface towards the zenith will be only 1/2 of that from a horizontal leaf of the same area

There will of course be lateral radiation from a vertical leaf

If the plane of the leaf is inclined at 60° to the horizon then it exposes to the zenith one half of its own area and consequently approximately radiates from an area about equal to and consequently the intensity of radiation from each unit of area of the leaf is about one half what it would be if the leaf were horizontal

Mem. Cosines of angle to horizon