Shallow Peaty Soil underlaid by Rock.
As the rock weathers away and becomes flatter the vegetation described above becomes more and more abundant until finally a considerable layer of peat results, which supports a plant population different in many respects from that of the original rock. Te Whakaru Island offers an example of such a station, and exhibits the gradual change from the lowly vegetation of the flat ground close to the sea to the grove of O. traversii on the higher ground, many of which trees are of the largest size to which that species can attain. The open parts of the island are covered with a dense carpet of Mesembryanthemum australe, some of which have red and some green leaves. Here and there where the latter has not taken possession, especially in the rather moist places, are patches of turf consisting of Crantzia lineata, Triglochin striatum, Cotula muelleri, Pratia arenaria, Selliera radicans, Schœnus sp., and Ranunculus acaulis. Sometimes the Pratia forms large patches unmixed with any other vegetation. Where the surface of the ground is higher and the soil probably deeper grows the endemic Cotula featherstonii (Plate XIV.). This plant forms large colonies on the dry peaty ground in which the mutton-birds make their holes, probably the presence of the birds' manure defining the habitat of the plant. It possesses a stout, smooth, upright stem, 13 mm. or more in diameter, which gives off about five branches rather close together, which latter again branch in a similar manner, the whole plant being from 15 cm. to 30 cm. in height. The leaves are soft and slightly succulent, but not sufficiently so for water to be squeezed out of them. They are crowded into rosettes at the extremities of the branches, the internodes being very short. The whole plant is of a greyish colour, and puts one in mind of the biennial stock (Matthiola incana). The roots are stout, strong, and woody, and form, with their rootlets, a mat, which lays hold firmly of the adjacent soil. As to the duration of life of C. featherstonii, there seems little doubt but that the plant is a perennial. At Maturakau Myosotidium nobile grows in large clumps near those of C. featherstonii (Plate XV.), all the rest of the ground being covered by Mesembryanthemum australe, which also hangs in sheets from the adjacent cliffs. On Te Whakaru Island a few plants of Phormium tenax on the peat and others on the rocks testify to the former greater abundance of this plant;
indeed, the whole formation, especially as seen at Te Whakaru, must have been enormously modified.