The Adventive Flora of the Chatham Islands By E. A. Madden and A. J. Healy [Received by the Editor, January 8, 1959.] Summary All previously published work on the adventive flora of the Chatham Islands has been reviewed, and a tabulation showing the evolution of the adventive flora is included. One hundred and fifty-three species and five varieties are now listed, compared with 28 species in the last formal listing by Kirk in 1873. Four species indigenous to New Zealand proper are cited as adventive in the Chatham Islands. The Chatham Islands were discovered in 1791 and their botanical history commenced with Dieffenbach's visit in 1840. This collection, which is treated in Hooker's Flora Novae-Zelandiae (1852–55) contained no adventive plants. Formal history of the adventive flora commenced with the incidental publication by F. Mueller of a small number of species in 1864, based on collections and notes by H. H. Travers, in 1863. It is reported (Cockayne, 1902: 254) that the invading Maoris in 1835 introduced potatoes, taro, and kumaras, and that gardens and orchards were established by the German missionaries after their arrival in 1843. He notes also (p. 255) that “…. with the fruit-trees came over a grass, Mr. Shand informs me. This I have not seen, but it was probably one of the first introduced plants to spread spontaneously on the island.” Livestock were first introduced in 1841, but it was not until 1866 that the present type of sheep stations came into being, when the sheep numbers were about two thousand, although cattle were stated to be wild in the “early sixties”. That opportunity for the establishment and spread of adventive plants had long been present is evident, for Cockayne (1902: 255) writes, “…. herbivorous animals have roamed almost at their own sweet will ever since the first introduction, and where, moreover, much of the vegetation has been burnt again and again, hardly any of the plant covering can still be in its virgin condition”. Kirk (1873: 320–21) on the other hand instances the great distance of the islands from the mainland of New Zealand, the limited intercourse with other areas, and the short period over which cultivation was carried on as limiting the scope for introduction and his consequent small list of adventive species (28 species), and notes only Rumex acetosella L. as generally distributed throughout. Dealing with the same point almost thirty years later, Cockayne (1902: 306–7) writes, “All the same, speaking generally, I do not think introduced plants have taken possession of the soil to anything like the same extent as in both Islands of New Zealand,” and mentions Rubus fruticosus as apparently the only species which is a menace to