[125]

Sept 7/ 79/ Seedlings of Phalaris raised in common garden soil & exposed before bright P. Lamp for 8° 30', so that they whole upper part had become parallel to soil — had not left furrow behind them & were vertical beneath the ground, & this no doubt due to mechanical resistance — of soil — Begin by saying it is quite necessary for following observations that the earth shd be covered with layer of easily yielding sand.—

[126]

No wrinkling even when upper & lower ends of Cot. bowed so as to be parallel.- Cell-walls must be highly elastic.

[126v]

is rendered

This vi

tween

observed seen by

& sub-

sexual

selectio

(with respect to the

primarily depend

primarily depend on

[Fragment of a draft of Descent 2: 295: "The probability of this view is strengthened by the differences in colour between the sexes occurring almost exclusively, as may be observed by going through the previous details, in those groups and sub-groups of mammals, which present other and distinct secondary sexual characters; these being likewise due to the action of sexual selection." This fragment is excised from CUL-DAR209.8.127v, below.]

[127]

Phalaris— Sept 7th 1879 7° 50' a.m 2 Pots Horizntal before Paraffin L. in dark to that so that Heliotrop & apogeotrop may act— to see whether basal bending is influenced by weight—

9° 50' more apogeotropic than Heliotropic but obliquely apogeotropic.

10. 33' I think have become heliotropic

11. 50' I am sure now much more heliotropic some have more twist from being first bent up by apogeotropy & now these tips [showing] heliotrop

1. 35 splendidly heliotropic mostly parallel to soil;

4. 30' parallel to soil most pointing to light & a little upwards. Hardly a trace of apogeotropism except in lower part of older Cots

Younger one as much bent close to base, as any I ever saw

[127v]

58 60

Chap. 17 18 Mammals.— Colour.

ew, more probable, that from the differences in colour be

the sexes occuring almost exclusively, as may be

going through the previous details, in those groups

groups of mammals, which present other secondary sexual

characters; & these are equally indicating ive of the action of sexual

n.] probability of colour having been modified through sexual selection, this will

It is almost superfluous to remark that quad =

which fact

[This fragment of a draft of Descent joins CUL-DAR209.8.126v, above]

[128]

Sept 7th 7° 50' a.m. — 2 Pots with seedlings Phalaris — raised in darkness— placed horizontally & left for 8°. 30' before paraffin lamp. They cd be acted on by apogeotropism & Heliotropism.— After 2° the former had acted much more than latter & they cd much upturned, yet obliquely towards light.— — After another 1° more heliotropic ie whole upper parts more turned towards light — In 4° after exposure it is certain that far more heliotropic— After 5° splendidly heliotropic very many with whole upper part parallel.— After 8° 30' from exposure— all younger ones parallel to soil & extended almost horizontally with only a trace of apogeostro, for they were a trace upturned, ie not quite strictly in direction of Light.— I have never saw seen cots more abruptly bent close to ground than several scores of these, & here weight of upper & first bowed part can have done absolutely nothing in causing flexure of lower ↘

[128v]

part, for weight weight acted at right angle to line of flexure.

I think it will suffice to give this one case.—

It is odd that apogetropy shd act earlier than heliotropism, but ultimately with far less effect

It occurred to us thus possibly weight of overarching or overhanging upper part might play an important part in the abrupt curvature of lower part, but numerous observation showed us that effect of weight quite unimportant.