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Heft I Arbeiten — Wurzburg (Radicles) & at end about Anisotropy

p. 145. Vines action of light on unicellular organs — believes growth less rapid on side exposed to light.— My facts on transmitted effects seem very important as showing something distinct from direct action of light — Show it is not merely direct action.

Heft III

p. 384 Prantl — Light retards growth of leaves as of internodes. (As Pfeffer remarks the incurved or retarded ⸮ growth of a whole is a different consideration from the differential retardation.) But it does not follow that this is the cause, & in the case of the quotidian periodical movements, which clearly stand in relation to alleviation of light & darkness, we cannot simply explain the result as due to light & darkness, as some leaves turn up & some down.

Sachs. p 398 & 394 the part which of radicle of Beans which bends easiest, has ceased to grow— the growing part stiff.— small elasticity

[Movement in plants, pp. 130-1: "The radicles did not present the appearance of having been subjected to a sufficient pressure to account for their curvature; and Sachs has shown* that the growing part is more rigid than the part immediately above which has ceased to grow, so that the latter might have been expected to yield and become curved as soon as the apex encountered an unyielding object; whereas it was the stiff growing part which became curved.
* 'Arbeiten Bot. Inst. Würzburg,' Heft iii. 1873, p. 398."]

— 397 growing part 8-10 m.m long p. 415

398 wetting one side increases its growth

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402. Sachs curvature with woodcut.

411. After 24˚roots in damp air behaves abnormally.

427 rate of growth of root changes with age

430 — on force by which root penetrates ground, he compares with nail driven into wood says almost impossible to estimate force

432 never speaks of transverse strain — experiments on quicksilver — says merely great

433 effects of cutting off 1 to .05 millimeter of tip of radicle — turn either upward or downwards— Put note may possibly be effect of irritating sensitive point.—

437 Effects of pressure on radicle

438 with Pea will make Circle. — like tendrils — so on aerial roots of Cercus. — The spot where pressure applied 1 to 2 m.m behind root-cap; as if grew hinder part rubbed— The part which grew & bent was that alone pressed against needles

[Movement in plants, p. 156: "The radicle of the common pea at a point a little above the apex is rather more sensitive to continued pressure than that of the bean, and bends towards the pressed side.*
* Sachs, 'Arbeiten Bot. Institut., Würzburg,' Heft iii. p. 438."]

p 440 a Horizontal radicle resting on needle bends

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Sachs Heft IV.

p. 609.— It is certain that side roots geotropic, but to act thus they must be constantly moistened. (I may have failed from this cause in my sensitive experiments

610 the bending region of 12˚damp roots 2-6 m.m.— They do not tend to point vertically down — p. 617 repeated again adaptation.

[in margin:] My Theory.

(N.B all organs are moving in every direction, & they can be made to mov move in any direction which is advantageous but under certain conditions, which serve as a guide to the plant.— No doubt light checks growth, but this is only a subordinate accident, which has to be overcome or increased.)

615— the bending from geotropism in secondary roots occurs before roots break out of main root

616 root-cap does not prevent bending of tip.—

[Movement in plants, pp. 154-5: "Sachs has shown* that these secondary roots are acted on in a peculiar manner by geotropism, so that if displaced they reassume their former sub-horizontal position, and do not bend vertically downwards like the primary radicle. Minute squares of the stiff sanded paper were affixed by means of shellac (but in some instances with thick gum-water) to the tips of 39 secondary radicles of different ages, generally the uppermost ones. Most of the squares were fixed to the lower sides of the apex, so that if they acted the radicle would bend upwards; but some were fixed laterally, and a few on the upper side. Owing to the extreme tenuity of these radicles, it was very difficult to attach the square to the actual apex. Whether owing to this or some other circumstance, only nine of the squares induced any curvature.
* 'Arbeiten Bot. Inst., Würzburg,' Heft iv. 1874, p. 605-617."]

619 Secondary roots in soil bend hither & thither, & this due to roughness in soil, for in air or water grew straight. As I have proved they are sensitive, this is important

621. geotropism ceases to act after secondary roots have become oblique.

622 if main root cut off, the secondary roots above will bend almost vertically down — like a side shoot of a tree will bend up — what adaptation!

[Movement in plants, p. 186: "Sachs has shown that the lateral or secondary radicles of the bean, and probably of other plants, are acted on by geotropism in so peculiar a manner, that they grow out horizontally or a little inclined downwards; and he has further shown* the interesting fact, that if the end of the primary radicle be cut off, one of the nearest secondary radicles changes its nature and grows perpendicularly downwards, thus replacing the primary radicle.
* 'Arbeiten Bot. Institut., Würzburg,' Heft iv. 1874, p. 622."]

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Sachs Heft IV.

630 "side roots of the 2d order" were never seen to be acted on by geotropism.— run very sinuous in the soil— Bean

631. when side-roots of 1st order are moderately geotropic the side roots of 2d order shows sign of are feebly geotropic, as with Zea

631 explains how the degree of geotropism in the different roots are advantages to plant

p. 620 I remember that he says individual roots on same plant bend differently & continually act in same manner— This must have been in centrifugal experiments—

(Where are his experiments with moist surfaces I suppose in Lehr buch— I must abstract.

[Movement in plants, p. 196: "But Sachs has proved* that the secondary radicles, or those emitted by the primary one, are acted on by geotropism in such a manner that they tend to bend only obliquely downwards. If they had been acted on like the primary radicle, all the radicles would have penetrated the ground in a close bundle. We have seen that if the end of the primary radicle is cut off or injured, the adjoining secondary radicles become geotropic and grow vertically downwards. This power must often be of great service to the plant, when the primary radicle has been destroyed by the larvae of insects, burrowing animals, or any other accident. The tertiary radicles, or those emitted by the secondary ones, are not influenced, at least in the case of the bean, by geotropism; so they grow out freely in all directions. From this manner of growth of the various kinds of radicles, they are distributed, together with their absorbent hairs, throughout the surrounding soil, as Sachs has remarked, in the most advantageous manner; for the whole soil is thus closely searched.
* 'Arbeiten Bot. Institut, Würzburg,' Heft iv. 1874, pp. 605-631."]

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Sachs — Heft III.

442— whole growing region bends down through geotropism.— root resting on support

44 56 The bent part of root in air or water flattens itself p. 456 by subsequent growth on under side. — This perhaps explains curvature lessening in my experiments with square of card. —variation in curvature in roots under similar conditions —

446 curvature not so great in air or water as in loose earth.

448 roots growing on flat plate, become arched, but do not turn up & away, as I shd have expected & therefore I suppose geotropism stronger than my curvature — I think cause of curvature in the drawing may be due to my curvature; No p. 452, because takes same form when growing in quicksilver.

450.1 Power of root to lift weight in being downwards can lift only a gramme.

456 believes that the rubbing of under side if radicle in the earth increases the bending downwards. Remarkable that this must strengthen the geotropic growth downwards, & as I saw when passing beyond ends of slips of wood

[Movement in plants, p. 198: "After a radicle, which has been deflected by some stone or root from its natural downward course, reaches the edge of the obstacle, geotropism will direct it to grow again straight downward; but we know that geotropism acts with very little force, and here another excellent adaptation, as Sachs has remarked,* comes into play.
* 'Arbeiten Bot. Inst., Würzburg,' Heft iii. p. 456."]

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Sachs. III. Heft.

459 infers (only) that a radicle must nutate because when placed apparently quite upright geotropism acted on them.

461. when bending from geotropism growth of upper sides as strong or stronger than normally, whilst that on lower side checked — This is exactly reverse of what occurs with a downward bent stem. Ciesielski found cells on upper side of r. of Pea longer & those on lower side shorter than in straight growing root— "Stengel" of Hipparia is geotropic like a root

p 463 & 465 cause of curvature mainly lies in weakened growth of under side

469 geotropism not destroyed by tips being cut off. ✓

Heft IV.

586 He calls roots when Hairs begin, as surfaces not here cuticularised.—

592 in aerial roots, growing region 10 times as long as in subterran roots. +

605 Secondary roots of the first order are acted on slightly by geotropism, but in peculiar manner, so that they never tend to grow vertically down.