My view, that the early Hawaiian Lobeliaceæ acquired the monstrous form of their flowers in the humid forests of a later age, is supported by the observations of Mr. Perkins on the connection between the highly-specialised nectar-eating Drepanids of Hawaii and the highly-specialised flowers of the Tree-Lobelias, a subject further discussed in [Chapter XXXIII.] This naturalist ascertained, in the case of one of the trees, that fertilisation could only be effected by these birds. So close is the biological connection between the Drepanid and the Tree-Lobelia, that Mr. Perkins finds here in part the cause of the development of the most remarkable forms of the birds. The botanist, also, would not dissociate the plants from this conclusion. There would be every reason to look for abnormal growth in birds and plants when the bird depends on the flower for its food, and the flower is dependent on the bird for its pollenisation. It is through such guises that the zoologist and the botanist have to penetrate when establishing the systematic affinity.
NOTE 81
On the Vertical Range of some of the most Typical and most Conspicuous of the Plants in the Forests on the Hamakua Slopes of Mauna Kea, Hawaii
During a descent of this mountain on its north side to near Ookala, the conditions were unusually favourable for recording the range of altitude for some of the plants easily recognisable.
Acacia koa began at 6,700 feet, and extended down to 2,300 feet.
Rubus (“akala”) began at 6,500 feet, and extended down to 2,500 feet.
Cheirodendron (“olapa”) began at 6,400 feet, and extended down to 2,200 feet.
Cyanea, a lobeliad growing on trunks of tree-ferns, began at 4,000 feet, and extended down to 2,300 feet.
Freycinetia began at 3,850 feet, and extended down to 2,000 feet.
Asplenium nidus began at 2,800 feet, and extended down to 2,200 feet.
Aleurites moluccana began at 1,800 feet, and extended down to 50 feet.