(1

1878. Sept 26

Phalaris — Action of Light.

after exposure to Darkness & Light

One pot of young seedlings all raised in darkness kept perfectly dark— another pot exposed yesterday in greenhouse, dark cloudy day, to light from above & this morning bright to same light. —

At 10. 20', both pots placed 38 inches before study N.E. window with linen & muslin window blinds down.— a towel & (bright-blue sky—) over case. — Sides blackened paper— roof & back protected by dark cloth.

10. 48 no effect

11º 10— Perhaps after 50' pot which hadbeen dark just perceptibly curved to light.—

11. 30 tips in dark pot certainly curved curved to Light; not so in other pot.—

11. 45 do—after 70' (I suspect one or 2 in other pot a little curved) (Put muslin blind over) (when momentary examined both pots held at right angle to dim light)

12º after 100m a conspicuous difference between the 2 Pots, especially when looked down on from vertically above; but certainly some of the shorter seedlings in Light pot a little curved to light.

12º 30' to 12º. 35' ie aft 2 h. 12, 132 m. angle of chord of 3 seedlings in dark pot, (in every case the most curved selected) 18º, 25º1/2 1.5 1/2 — mean 19º.7 — Also of 4 most curved in light pot. 2º.5', 11º, 5º, 8º, = mean 6.6.

1º. 33'— to 1º.43' say 1º 40' (ie after 3h 20m) (always placed at right angles to light when observed.)

(Mostly the same seedlings remeasured but not always)

Dark Pot. 16º 13º 23º 17} mean 17.2

Light Pot 9º 5º 8º 1/2 10} mean 8º

2º 30' to 2º 35 say after another hour

Dark Pot 11 22 17 1/2 20} mean 17.6

Light Pot 8º1/2 10º 7º 9º} mean 8.

Distance of Pots from N.E. window

(over)

[94v]

At 2º. 35' As a [illeg] pots placed in complete darkness & at 4º. 30' in Light Pot hardly a trace of curvature; in Dark Pot upper part of seedlings still curved considerably to Light.— Now the Conclusion It is therefore certain that plants C brought out of moderate brightness curve much less within same time to light than those which hadbeen kept in complete darkness. — Whether they move sooner cannot be told for if they had begun at same time the lesser movement of those which hadbeen in brightness would not have been so soon distinguished.—

(2

Sept 28' 1878.

Phalaris:— Action Light

After exposure to darkness & light

Both pots with seedlings raised in darkness.

10º 30' a.m— A pot exposed yesterday & this morning to daylight— sky cloudy all time, but high & light, & another pot in complete darkness— but seedlings not very straight, (some gleams must have come in, but I arranged them so that next now now light wd com in transversely.— transversely

Box covered with 2 towels - window & muslin blind down day high light clouds.

10. 30 exposed

11º 24' (ie after 54') no difference

11º 40— Dark pot, alone tips distinctly ie. after 1º 10' (or 70') curved to light—

12º. 6' ie. after 1º 36' do. do. do do

11º 40'

12. 30' ie after 2º — 10' I think perhaps tips in Light pot just perceptibly curved to L.

12. 55 Light pot certainly certainly certainly with tips curved a trifle to Light.— great — grt ie. after 2º 25' difference between the 2 Pots

1º 43— grt difference between the 2 Pots

2º. 15 angles taken; in pot which hadbeen in Light angles of 3 averge seedlings were 8º, 4º 1/2, & 3º = 5º mean.—

In Pot which hadbeen in dark angles of 3 average seedlings were 12,º 19º, & 17º — mean 16º — (chords were taken with horn protractor from tip to base.)

(We now know that seedlings which havebeen treated alike in equal time, those exposed to brighter light are most curved — Also that seedlings exposed for equal times which had previouslybeen exposed to light from above not causing curvature are differently affected by same degree of obscure Light.—

Effects of Light transmitted in time.

(2

Sept 29' 1878 Action of different degrees of light.— at different distances

Phalaris

Seedlings raised in darkness— too tall

I can now see that it is necessary that seedlings of same height shd. be compared & left only for 3 or 4 hours

(Five Pots exposed at 8º 26' a.m to Hall-Lamp in darkened room at (1) 1 ft, (2) 2 ft, (3) 4 ft, (4) 5 ft & (5) 6 ft.—I ought to have 10 I could read my watch at all distances, though I cd not see seedlings in Pot 5.— I could read larger Type in Cross-F Form of Flower Forms of flower only by Pots (1) & (2) — By Pot (2) I cd read smaller type with much difficulty.— After 1º no effect — At 10º ie after after 1º 34' tips in all 5 Pots I think a little curved.

At 11º no doubt all curved. aft 2º 30'

At 4º 40' (ie after 8º 14') compared all pots in a row seedling in (1) & (2) plainly more curved then in 3 other pots in which no marked difference. Shows with time very dull light causes considerable curvature. I measured angles, of chords of bent seedlings but they go for nothing

Pot (1) (at 1 ft {49º from the perpendicular 47 40º taller 20º still taller

Pot 2 {40 26º taller

Pot 3 {20º 38º

Pot 4 {17º 15º

Pot 5 {16º 32º

I have looked again those in Pot (1) more curved than in (2) — not nearly so much difference between 2 & 3 as I shd have expected, & but little difference between (3) & (5) & yet (5) received only 1/36 of light; I suppose length of time made up for less action.

[in margin:] 2 ft 4 ft 6 f 8 ft 10 ft I ought to try