THE DISPLACEMENT OF SPECIES IN NEW ZEALAND. 347 and robust growth of the herb, which is not infrequently from 3 ft. to 5 ft. in height above the water-level, and often impedes the passage of boats. This luxuriance is chiefly due to the mildness of the climate, and has a singular parallel in one locality in England. At the Wyken CoUiery the water pumped up from a great depth is of a high temperature, and flows into a stream which expands into a large, shallow pond. As the pond is never frozen, even in the severest weather, the watercress is almost as luxuriant as in New Zealand. The Canadian water- weed [Anacharis Alsinastrum) simply chokes the River Avon at Christchurch, and has been carried by aquatic birds to other streams in Canterbury and Otago, but is rare in the North Island, being restricted, so far as known to me, to a river near Mongonui, and another in the Bay of Plenty. It is of considerable interest, owing to its being the only submerged aquatic plant that has become naturalized in the colony. Naturalized Fungi. Several naturalized fungi are highly injurious to the indigenous vegetation, as the ergot {Claviceps purpurea), which infests numerous native grasses; the clematis cluster-cup {^cidium clematidis) fre- quently infests Clematis Colensoi and other species almost to the point of destruction, the stem, petiole, and even parts of the flower becoming thickened and distorted under its attacks : but the limits of this address will not permit me to enter into detail. Rate of Increase. As the number of species more or less completely naturalized in the colony is upwards of five hundred, it becomes a question of some interest whether additions will be made to the catalogue at the same rate during the next half-century as in the past ; if so, the number of species of naturalized and indigenous Phanerogams would be about equal, and many of the latter would be crowded out of the field. A satisfactory answer may, I think, be given. The first catalogue of naturalized plants was published in the original Flora of New Zealand, ii. 321 (1855). It comprises sixty- one species, seventeen of which must be excluded as erroneous, leaving forty-four naturalized species. The second list, published in the Handbook of the New Zealand Flora, 757 (1867), contains 171, from which twenty-one species must be deducted as included on insuflScient grounds, leaving 150 species naturalized. A list prepared by the present writer was published in Transactions of the New Zealand Institute, ii. 131 (1869) ; it embodied all that was then known on the subject, and enumerated 292 species, a summary of which, given at p. 146, showed forty-one species erroneously in- cluded, or of uncertain position, and 251 species truly naturalized. During the three following years I added fifty-three species to the list, making a total of 304 species known to me at the date of my ceasing to reside in Auckland. In 1882 Mr. Cheeseman pubHshed a list of the naturalized plants of the Auckland district, in which he raised the total to 382 ; but this does not include a few species seen by myself, and still unpublished. At the present time the number 2 A 2
