[85]

Geotrop Tips naked basal part Basal part painted part

(Examined at 11° a.m Sept 2d.)

ie exposed to apogeotropism since 5° P.m yesterday

I now Know that the crust of Indian ink makes stem rigid, so that lower parts cannot bend.

(1) whole quite upright (short & young)

(2) whole do (rather short)

(3) rather longer— upper part curved — lower part strong — I suspect originally inclined

(4) lower part straight — upper part curved

(5) lower whole straight

Upper part painted — lower part naked

(1) greatly curved — Horizontal, but I think curvature is in lower part also

(2) do do almost horizontal — curvature confined to lower part.

(3) lower part only slightly inclined— upper part straight

(4) lower part greatly curved — upper part straight.

[in margin:] As basal part bends last, (perhaps paint being injurious acts only by checking the bending of this part.)

(5) — lower part very slightly curved — upper part straight

(As quill at base does not prevent upper part of Oats bending up — cannot be rigidity.)

It follows that when upper half painted, though injurious action, if any, has acted longer, the basal half is acted on by apogeotrop— Whereas when basal half is painted, it cannot bend because(?) so rigid from paint the injurious action, if any, has prevents any part being at all or much acted on by apogeotropism, but this applies chiefly to very young specimens. Moreover the upper parts were a little curved to light & thus have become straight through apogeotropism.

781 (637A)

Ch Xll

extent, & why if the differentiation be carried still further injury follows. It is an extraordinary fact that with many species, flowers fertilized with their own pollen are either absolutely or in some degree sterile; if fertilized with pollen from another flowers on the same plant they are sometimes though rarely a a little less sterile; more fertile; if fertilized with pollen from another individual or variety they are fully fertile' but if with pollen from other or allied a distinct species, they are sterile in all possible degrees, with absolute sterility is again reached. We thus have a long series with absolute sterility at the two ends; — at one end due to the sexual

[Cross and self fertilisation, pp. 455-6: "But the veil of secrecy is as yet far from lifted; nor will it be, until we can say why it is beneficial that the sexual elements should be differentiated to a certain extent, and why, if the differentiation be carried still further, injury follows. It is an extraordinary fact that with many species, flowers fertilised with their own pollen are either absolutely or in some degree sterile; if fertilised with pollen from another flower on the same plant, they are sometimes, though rarely, a little more fertile; if fertilised with pollen from another individual or variety of the same species, they are fully fertile; but if with pollen from a distinct species, they are sterile in all possible degrees, until utter sterility is reached. We thus have a long series with absolute sterility at the two ends;—at one end due to the sexual elements not having been sufficiently differentiated, and at the other end to their having been differentiated in too great a degree, or in some peculiar manner."]