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Oct 1. 1878   Phalaris   Degree of Obscure Light which will act

Exposed pot young seedlings in Franks darkened room to (2d) Hall-Lamp, (which unfortunately became dim at about 1° & had to be refilled) at distance of 12 ft. — at this distance I cd not see plants, nor read large figures (1/5 of inch high) on my watch with white face— nor a double pencil line, but cd see a narrow line with Indian ink.— could distinguish no shadow from pencil— — Exposed to the light at 7° 45' a.m.— at 9° 45' (ie. 2°) no effect— at 10° 45' (ie 3°) I think tips slightly inflated & Frank thought so to. — at 11° 4.5'— there cd be no doubt about curvature.— At 4° 25' 8° 40' plants removed & angles measured from the perpendicular of 5 seedlings— good average specimens of chord from tip to middle of base

11° rather tall

18 1/2°— rather short Seedling

21°

5 1/2 short seedling

24°1/2} mean 16°. (Used) 25 [+] 23 [=] 48

We have seed with seedlings from seeds sown at same time & of course treated in same way, how their degree of bending from Heliotropism differs, according to, & independently of their height— Moderately The tendency must be innately variable in extreme degree.—

Slowness of Action of Light