[379]

Dahlia 18

[Figure] not worth giving

Fig. — 23 Stapelia sarpedon

Pot moved to new position, but not altogether turned and [text excised]

June 26th [figure]

[380]

Fig 22 A

Stapelia sarpedon Circumnutation of Hypocotyl.

Fig

[Paper pasted on as CUL-DAR209.4.379]

(not size no lettering)

(Fig 23) (Movement Movement of Hypocotyl — seedling illuminated from above. Temp 23-24°C — magnified 21 times

48

[380v]

38 649

Chap. E 10

really been developed in correlation with the nectary. The two upper petals of the common Pelargonium are thus marked near their bases, and I have repeatedly observed that when the flowers vary & become by variation  peloric or regular, as not rarely happens, they lose their nectoaries and at the same time the dark marks. When the nectary is only partially aborted only one of the upper petals loses its mark. Therefore the nectary and these marks clearly stand in some sort of close relation to one another; and the simplest view is that they were developed together for a special purpose; the only conceivable one being that the marks serve as a guide to nectary. But from the remarks already made, it is clear It is, however, evident from what has been said that insects could discover the nectar without aid of guiding marks. They are of service to the plant only by fertilising allowing a greater number of visits by insects to visit & suck the flowers within a given period (to which subject I shall recur) than would other wise be possible; and thus there will be better chance of cross-fertilisation by pollen from

[Cross and self fertilisation, pp. 373-4: "The following case affords, I think, the best evidence that these marks have really been developed in correlation with the nectary. The two upper petals of the common Pelargonium are thus marked near their bases; and I have repeatedly observed that when the flowers vary so as to become peloric or regular, they lose their nectaries and at the same time the dark marks. When the nectary is only partially aborted, only one of the upper petals loses its mark. Therefore the nectary and these marks clearly stand in some sort of close relation to one another; and the simplest view is that they were developed together for a special purpose; the only conceivable one being that the marks serve as a guide to the nectary. It is, however, evident from what has been already said, that insects could discover the nectar without the aid of guiding marks. They are of service to the plant, only by aiding insects to visit and suck a greater number of flowers within a given time than would otherwise be possible; and thus there will be a better chance of fertilisation by pollen brought from a distinct plant, and this we know is of paramount importance."]