I.—Extent of Diffusion. With the view of indicating, as precisely as practicable, the present diffusion of each species, that Province of Auckland, as far south as Ngarua-wahia, has been divided (somewhat arbitrarily) into districts, as under:— 1. North Cape:—from Cape Maria Van Dieman and the North Cape, to Hokianga and the Bay of Islands. 2. Whangarei:—from Hokianga and the Bay of Islands, to Cape Rodney and the north head of the Kaipara harbour. 3. Waitemata:—from the south head of the Kaipara, and Cape Rodney, to the head of the Manukau harbour at Penrose, and the Tamaki at Panmure. 4. The Islands:—including the Cavalhos and Taranga groups, the Great and Little Barriers, etc., the Kawau, and those in the Firth of Thames. 5. Cape Colville:—the Cape Colville peninsula as far south as Kawæ-ranga and Wangamata Bay. 6. Waikato:—from Penrose and Panmure to Whaingaroa and Nga-ruawahia. The district in which each species is known to occur will be indicated by the use of the numbers prefixed above; thus practically affording a separate list of the naturalized plants of each district; but it must not be supposed that these lists are complete, even for any one district. The naturalized plants of the western side of the North Cape district are quite unknown to the writer, and to a great extent those of the western side of the Whangarei district. The districts for which the lists are most complete, are Auckland, the Islands, and Cape Colville. Very little is known of the naturalized plants of the western and extreme southern divisions of the Waikato district, or of the East Coast, south of Wangamata Bay. II.—Introduction Of Plants. This has evidently been effected by two chief causes; the direct agency of man, for the purposes of cultivation; and the indirect agency of man and the lower animals, etc. The first head may be sub-divided into:— 1. Horticultural (Hor.), * The abbreviations in parentheses are employed in the list.—ED. remains of, or escapes from garden cultivation, as Pelargonium quercifolium, Iris germanica. 2. Agricultural (Agri.), remains of, or escapes from, field cultivation, as Lolium perenne, Trifolium repens. 3. Accidental. (Acc.) Under this head are included those plants unintentionally introduced by man, whether mixed amongst seeds of ordinary cultivated plants, as in the case of buck-wheat, corn cockle, etc.; or from the seeds being able to attach themselves to clothing, or to the skins of animals, as the various docks, mallows, etc.; or from less prominent causes: in this way Erigeron canadensis has been carried all over the world. 4. Uncertain. (Unc.) Plants introduced by causes not directly referable to either of the above. III.—Degree of Establishment. As has already been stated, there is a wide difference in the degree to which naturalized plants have adapted themselves to the new conditions under which they are placed. It is attempted to estimate the extent of this adaptiveness by the application of the following terms:— 1. Denizen. (Den.) Plants thoroughly established, and spreading widely without assistance from man; often displacing indigenous forms to a great extent, or readily amalgamating with native species, as Trifolium minus, Erigeron canadensis, Poa annua.