[242]

Long straw – Roof

Young young Flower, head vertical

Trifolium subterraneum

July 23d

[data not transcribed]

[242v]

which has been differentiated by exposure to different conditions or through spontaneous variation. But the analogy fails when we turn turn to the negative or weak effects of pollen from one species, for it does not appear that although some substances which are extremely dissimilar, for instance, carbon and chlorine, have a very feeble affinity for each other, yet it cannot be said that the weakness of the affinity depends in such cases on the extent to which the substances differ. It is not known why different differentiation is necessary or favourable for the chemical attraction affinity or visible any more or union of two substances, any more than for the fertilisation or union of two plants.)

[243]

Trifolium subterraneum (Black Paper)

[data not transcribed]

[243v]

732 3 (18

Ch XI

visited by three bees In nineteen minutes each every flower on a small plant of Nemophila insignis was entered visited twice. In one minute six flowers of a Campanula were entered by a pollen-collecting hive-bee; and bees when thus employed they work slower than when sucking nectar. Lastly, seven flower-stalks on a fruit plant of Dictamnus (213) fraxinella were observed on the 15th of June 1841 for during ten minutes; and they were visited by 13 humble-bees each of which entered many flowers; on the June 22nd the same flower-stalks were visited within the same time by 11 humble-bees. This plant bore altogether 280 flowers and from the above data, taking into consideration how late in the evening humble-bees work, each flower must have been visited at least 30 times daily, & the same flowers keep open during several dail days. The frequency of the visits of bees to the same flowers, is also sometimes shown by the manner in which the petals are scratched by their hooked tarsi of the bees; I have

[244]

continued

Long Straw was on roof now on temporary Vertical glass

Trifolium subterraneum

[data not transcribed]

[244v]

738 (24

Ch XI

of the two. My son remarks "It is difficult to say how the bees could have acquired this habit. Whether they have discovered the inequality in the size of the nectar-holes in which sucking the flowers in the proper way, and have then utilised this knowledge in determining where to gnaw the hole; or whether they have found out the best situation by biting through the vexillum standard at various points, & have afterwards remembered its situation in visiting other flowers. But in either case they show a remarkable power of making use of what