Having thus prepared the way, I will proceed to the discussion of the Hawaiian Lobeliaceæ, dealing first with their “station.” Their vertical distribution is well illustrated in the large and lofty island of Hawaii. Whilst the woody Compositæ, as before described, are most at home on the open-wooded and often scantily-forested slopes between 5,000 and 9,000 feet, the Lobeliaceæ are most characteristic of the middle or true forest zone that extends from 2,000 or 3,000 feet to between 5,000 and 6,000 feet above the sea. This lies within the region of clouds and mists, and it is here that the rain-belt or area of greatest rainfall is situated, the annual amount averaging probably 150 to 200 inches. It is in such humid conditions that, as Hillebrand observes, trees and jungle are developed in greatest luxuriance; and it is here that “the Lobeliaceæ exhibit their most striking forms.” The traveller, as he ascends the mountains, finds the Tree-Lobelias in the region of mist and rain-cloud; and he is lucky if he escapes the usual downpour and encounters only a fine drizzling rain.

The mild climate of this region is indicated by a mean annual temperature ranging probably with elevation from 65° to 55° F. It is secure from the frosts of the upper slopes of the mountain; whilst at the same time it is above the regions of tropical heat. There is, however, no doubt that when the forests extended to the coasts, as they occasionally do now on the north side of Hawaii, the Lobeliaceæ occurred much lower down than they do at present, though still only attaining their greatest development in size and number in the higher levels. Thus, at rare intervals, I noticed in the forests of Hamakua and Kohala, where they descended to the coasts, species of Clermontia at an elevation of only 500 or 600 feet above the sea.

Probably in no part of the Hawaiian Islands are the conditions under which the “Tree-Lobelias” thrive better illustrated than on the higher slopes of Mount Eeka, a bulky mountain mass about 6,000 feet in height, forming the western portion of Maui. Its flat top, as Hillebrand observes, is wrapped in a cloud of mist nearly the whole year. On the boggy surface of the summit, where Acæna exigua gives a tussocky appearance, and Sphagnum or bog-moss abounds, flourish Cyperaceæ, Lycopods, and Selaginellæ; and here Drosera longifolia and a peculiar species of marsh violet (Viola mauiensis) find a home. The upper slopes, down to 4,000 feet, present similar moist conditions, and here in an open-wooded district, associated with Cyrtandræ, Marattias, and true Tree-Ferns, the ground being covered with Lycopods, the “Tree-Lobelias” abound. I noted four kinds within two hundred yards. Of the humidity of the upper slopes of Mount Eeka I have a very vivid recollection, and my experience of passing a night on that mountain is described in [Chapter XIX.]

The Lobeliaceæ, as Hillebrand remarks, occur invariably as isolated individuals. I was often struck, however, with the preference the genera showed for particular localities. Thus, Clermontia is well represented on the western slopes of Mount Eeka, Delissea on the northern slopes of Hualalai (3,800 to 4,500 feet), Cyanea on the Hamakua slopes of Mauna Kea (2,300 to 4,100), and Lobelia on the southern slopes of Mauna Loa behind Punaluu (2,000 to 3,500 feet).

To the student of geographical distribution the Hawaiian Lobeliaceæ are of especial interest. Mr. Hemsley observes that they have their greatest affinities in America (Intr. Bot. Chall. Exped., p. 68). M. Drake del Castillo, in his “Mémoire couronné par l’Académie des Sciences” (Paris, 1890), remarks that these plants connect Hawaii with America just as the Goodeniaceæ link the same group with Australia. This is what we might have expected since the centre of the order is in America, principally in the Mexican and Andine regions (Drake del Castillo, Flore Polyn. Franc., xi.).

Though five out of the six genera are endemic, the sixth, that of Lobelia, has a world-wide distribution. Here then, we have a genus that belongs strictly to the next or second stage of the plant-stocking of the Hawaiian Group, namely, when the non-endemic genera now containing endemic species were introduced. As with the Composite genera, Campylotheca and Lipochæta, Lobelia marks the beginning of the new or the close of the old era. It is, however, necessary to point out that many of the conditions favouring luxuriant and rank vegetable growth are pre-eminently represented in the zone of the Lobeliaceæ. In these soft-stemmed plants with their copious milky sap and large fleshy flowers, sometimes two or three inches long, the very redundancy of growth would tend both to exaggerate and to disguise the generic distinctions. To the ordinary observer these “Tree-Lobelias” call up vague notions of a flora of a bygone age, and by their bizarre appearance he might with some excuse be led to give play to his imagination when describing them; but the systematic botanist, seeing through their disguise, frames rather more prosaic notions of their antiquity and degree of differentiation. According to my view, the first Hawaiian Lobeliaceæ occupied open, exposed localities such as are held by the decadent genus Brighamia now, and acquired their monstrous form in the humid forests of a later age. (See Perkins in [Note 80].)

In his monograph on the Campanulaceæ (Engler’s Nat. Pflanz. Fam., teil 4, abth. 5, 1894), S. Schönland, speaking of the sub-family Lobelioideæ, places the seven endemic Hawaiian and Tahitian genera in a group by themselves. Though, as he observes, the Hawaiian tree-forms appear at first sight to constitute a natural group, they cannot be sharply distinguished from other forms, and even in habit come near some Indian and Abyssinian types of Lobelia. In their treatment, he says, they should all go together, and he does not approve of the endeavours of some botanists to isolate one of them (Brighamia) from the rest and to connect it with the Australian genus Isotoma.

It is also to be noted that whilst four of the Hawaiian genera are more or less dispersed over the group, one (Brighamia) with only one species is confined to the islands of Molokai and Niihau, the double habitat being suggestive of its approaching extinction. Another (Rollandia) with six species is restricted to the island Oahu. Cyanea, which possesses twenty-eight out of the total of fifty-eight species, may, from the point of view of its formative energy, be regarded as in its prime. It is thus apparent that, as with the Compositæ, the early Lobeliaceous immigrants were not all contemporaneous arrivals.

DISTRIBUTION OF THE LOBELIACEÆ IN THE HAWAIIAN ISLANDS.[[4]]

Hawaiian Lobeliaceæ.Brighamia.Lobelia.Clermontia.Rollandia.Delissea.Cyanea.Total.
Species confined to one island——6642238
Species confined to two islands122—2512
Species confined to three islands—12—115
Species generally distributed, but still endemic—21———3
1511672858