[86]

Sept 2d. 1878

Canary-grass— Seedlings Light.—

5 with upper half— painted & repainted with very thick Indian Ink— 4 with lower half painted — in dark Box before S.W. window— exposed at — 8° 50' examined at .4° 40. 5°

Seedlings rather tall, many rather above 1 inch high.—

4/5 All 5 of those painted above straight, from tip to base, but one is very slightly curved to L, & this has bare spot on light side.

Of the 4 with basal half painted the bases of all straight; the upper half of 1 much curved, & of other 3 slightly to L.

(5° 10' arranged in dark for apogeotropism.

10. 45' a.m Sept 3d, 3 taller ones with quite straight. — 4th rather tall whole length somewhat curved upwards 5th short or young one somewhat curved up.

The 4 seedlings with basal half painted quite upright—

I have ascertained by feeling that the crust by Indian ink gets so hard that it would probably prevent bending —

Painted useless

Indian Ink

[87]

Sept 19th 1878

Phalaris

Transmitted effects of light beneath ground.

Two Pots with seedlings were coated with the very fine araceous argillaces-arenean sand, consisting chiefly of very minute grains & silex, coated with oxide of iron: before exposing to light was watered with ether-spray & the fine sand close embraced closely round all the stem.— Plants exposed at 9° a.m & examined at 5° P.m. Course Greatly Greatly bent to Light, but not horizontal in any as I have sometimes seen them.

In almost every case, there was a furrow in the sand behind the stems or Cots: Placed under compound m. with weak power— These furrows beautifully distinct retaining outline of Cot: one side towards light no such crescentic furrow. & As far as I could measure with micrometer, (though this was difficult) the transverse diameter of crescent; was in 3 cases 10/500, 15/500 10/500 long ie 2/100 or 3/100 of inch long. I then cut through sand close to Cot in line of light of most several seedlings & it was clear that in 4 cases stems were curved to light for a depth of about 1/10th of inch beneath surface. A needle was then stuck close & parallel to part of stem which had been buried, & these needles formed formed angle of 11°, 13°, 15° & 18° from the perpendicular; These angles agree very fairly well with diagram on next P., but in the latter case the Cot. had protruded a little obliquely from seed, which was planted shallow. That, these inclinations Ø

[87v]

were due to transmitted effects of light was clear clear for next morning owing to apogeotropic the buried parts were nearly quite perpendicular. Nor in any case was there a crescentic furrow to leeward or on shady side of Cot. — but there was a slight crack all round due to circumnutation.

We cannot attribute this action to light penetrating penetrating the sand, for a thickness thickness of 1/10' of inch placed on glass quite excluded light—: even 1/20th let in so little light that from other experiments I feel sure wd have had no effect.—

Some seedlings Oats exposed similarly covered with to line of sand had a slight crescentic furrow to leeward or on shady side; but the basal part of Oats-Cots: does not become so much bent as in case of Phalaris.—

[diagram with calculation]

(2

1878

Phalaris — Light

Sept. 27th 8° 20' a.m fastened externally with 3 fine threads & shell-lac thin rigid hollow glass tube rods to about upper half of 6 cotyledons & exposed in black box to S.W window, to see if rigidity of upper half, prevents lower half bending to light, as many scattered & some direct observations make me believe suspect.

Examined at 4° 40' — all six somewhat curved to light, & several seem in close apposition filament or rod— but of these lower parts are not so much curved as the free ones, of course the upper tied portion is straight— the sole use of these observations will be to show that constraint does not stop all bending to light.