[139]

April 7— 63.— Adoxa — The upper flower has its 4 petals placed in angles between the 4 closely surrounding lateral flowers. These latter which have 3 sepals, have 2 of them on upper side forming a fork, & in one fork at one end of head & in other fork at other end, the 2 sepals of upper flower lie resting.

It certainly seems as if the varying parts in the upper flowers had been determined by the adaptation of packing to the surrounding 4 flowers.—

[Origin 5th ed., p. 154: "In the British Adoxa the uppermost flower generally has two calyx-lobes with the other organs tetramerous, whilst the surrounding flowers generally have three calyx-lobes with the other organs pentamerous; and this difference appears to follow from the manner in which the flowers are closely packed together. In many Compositæ and Umbelliferæ, and in some other plants, the circumferential flowers have their corollas much more developed than those of the centre; and this is probably the result of natural selection, for all the flowers are thus rendered much more conspicuous to those insects which are useful or even necessary for their fertilisation."]