[311 and 312]

Oxalis rosea

June 17th

(A) 17°

Oxalis rosea circumnutation of Cotyledon Hypocotyl secured?

Fig. 13B

(reduced to 1/2 Scale (some lettering))

Circumnutation of Cotyledon, with Hypoy secured— seedling observed from above

Reduce to 1/2 origin scale

[312v]

37 648

Chap. E 10

being more intense and thus less readily obliterated. Sprengel's notion of the use of these marks appeared to me for a long time a fanciful one ; for insects without this aid readily discover and bite holes through the nectary from the outside. They readily also discover the minute nectar-secreting glands on the stipules and leaves of certain plants. which secrete a sweet fluid. Moreover some few plants, such as certain poppies, which are not nectariferous, have guiding marks; but we might perhaps expect that some few plants would retain traces of a former nectariferous condition. On the other hand these marks are much more common on asymmetrical flowers, the entrance into which would be apt to puzzle insects, than on regular flowers. Sir J. Lubbock has also proved that bees can well readily distinguish colours, and that they lose much time if the position of honey which they have once visited is be in the least changed.* (*British Wild flowers in Relation to Insects. 1875. p. 44) But The following case affords, I think, the best evidence that these marks have

[Cross and self fertilisation, pp. 372-3: "In the white varieties of many flowers, such as of Digitalis purpurea, Antirrhinum majus, several species of Dianthus, Phlox, Myosotis, Rhododendron, Pelargonium, Primula and Petunia, the marks generally persist, whilst the rest of the corolla has become of a pure white; but this may be due merely to their colour being more intense and thus less readily obliterated.
Sprengel's notion of the use of these marks as guides appeared to me for a long time fanciful; for insects, without such aid, readily discover and bite holes through the nectary from the outside. They also discover the minute nectar-secreting glands on the stipules and leaves of certain plants. Moreover, some few plants, such as certain poppies, which are not nectariferous, have guiding marks; but we might perhaps expect that some few plants would retain traces of a former nectariferous condition. On the other hand, these marks are much more common on asymmetrical flowers, the entrance into which would be apt to puzzle insects, than on regular flowers. Sir J. Lubbock has also proved that bees readily distinguish colours, and that they lose much time if the position of honey which they have once visited be in the least changed.* The following case affords, I think, the best evidence that these marks have really been developed in correlation with the nectary."]