Lepidium sisymbrioides make spots of very dull chocolate, which are confused in the general scheme with the paler browns, dull greenish-yellows, and greys, of Oreomyrrhis andicola, Myosotis decora, Anisotome Enysii, &c. The sparsely scattered plants of Ranunculus paucifolius become almost invisible in this environment, and play no leading part in determining the appearance of the whole unit. The whole effect is most peculiar; the calciphile flora gives the impression that it belongs elsewhere—to another age, another climate and country. Much the same effect is produced, in my experience, by the isolated patches of ancient fen vegetation which survive at such spots as Wicken and Cottenham, set like savage aliens of some older and vanishing race in the midst of the green crops and pastures of modern Cambridgeshire.

(c.) As the formation becomes more nearly closed, on the borders of the grassy closed areas, Plantago spathulata appears in great quantities, and the closed formation of the immediate neighbourhood includes Festuca novae-zelandiae, two or three others of the usual grasses of the district, Raoulia subsericea, Hydrocotyle novae-zelandiae var. montana, Vittadinia australis, and a fair amount of moss. Here occasional plants of Lepidium sisymbrioides appear, but not far from the pure limestone patches.

(d.) The chief introduced plants which occur in the basin are Arenaria serpyllifolia (extremely abundant everywhere—more so than any native plant), Cerastium glomeratum, Hypochaeris radicata, the large ox-eye daisy (which completely covers the slopes on the eastern side of the rocks outside the basin), and Verbascum Thapsus. It is not without significance, as showing the very special and peculiar character of the locality, that Hypochaeris radicata, elsewhere so exceedingly abundant in New Zealand, is here comparatively rare.

It must be added that the rocks above the basin and the steepest slopes around them also harbour Epilobium gracilipes (which never occurs on the flat), Senecio Haastii (which is comparatively seldom seen below), Senecio lautus var. montanus, and a good number of such shrubs as Coprosma propinqua, Discaria toumatou, and Aristotelia fruticosa. Upon these shrubs the peculiar parasite Korthalsella clavata is found; this also grows upon shrubs in other limestone rocks (e.g., those at the junction of the Porter and Broken Rivers), but apparently is found only in the Castle Hill district.

A certain number of these plants are definitely calciphiles, and occur in no other situations; others seem to grow by preference on limestone, but are not confined strictly to it (in this district, at any rate); and the rest are of general distribution.

In the first class are Ranunculus paucifolius, Poa acicularifolia, Korthalsella clavata, Epilobium gracilipes, Myosotis decora, Anisotome Enysii. In the second are Oreomyrrhis andicola var. rigida and Crepis novae-zelandiae.

Several of them exhibit marked xerophytic characters, as described by Cockayne and Laing (Speight, Cockayne, and Laing, 1911, p. 358), and among these Ranunculus paucifolius is conspicuous. It has the pale ashenpurple colouring which distinguishes the shingle-slip plants generally, such as its relations Ranunculus chordorhizos, R. crithmifolius, and R. Haastii, Lepidium sisymbrioides has special adaptations, of which the disproportion ately long root is most remarkable (Cheeseman, p. 42). Anisotome Enysii shows a colouring very similar to that of Ranunculus paucifolius. There is here a marked degree of epharmonic convergence.

These plants make up a community of intense interest, and the problem of their existence is bound up with that of Ranunculus paucifolius, whose limited distribution and feeble powers of reproduction help to put that problem in a clearer and more striking light.