10 



endemic element; (2) the absence of species more or less char- 

 acteristic of adjacent botanical districts; (3) the presence of 

 species of restricted distribution elsewhere; (4) the presence 

 in abundance of widespread species much rarer elsewhere; (5) 

 the relative abundance of the various species comprising the 

 florula; (6) the general physiognomy of the vegetation ; (7) the 

 presence of special characteristic plant-associations; (8) the 

 differences in widespread plant-formati ons ; (9) the agriculture, 

 horticulture, and introduced plants of the proposed area." 



As pointed out in the original article, the "actual boundaries 

 of many of the districts are extremely hard to fix and in no few 

 cases must always be artificial." This leads up to an inquiry as 

 to how far, based on four years' trial of these districts, sup- 

 plemented by a good deal of field-work in the South Island, the 

 boundaries, etc., of these districts should be modified. 



Taking the North Island first of all, it is a moot point 

 whether or not latitude 36deg. S., a most critical point, as 

 explained later, should not be made a boundary-line and the area 

 to the north be constituted either a district or a subdistrict. 

 As for the boundary of the South Auckland District the Mokau 

 River would probably be more natural than that shown on the 

 map. The Volcanic Plateau and, East Cape Districts seem 

 natural enough, but their limits require extended study in the 

 field. Probably the southern boundary of the East Cape 

 District should be moved further to the south. The southern 

 part of the North Island offers exceptional difficulties. It can- 

 not be right to treat it as one district, and yet, according to the 

 present arrangement, the Egmont-Wanganui district is based 

 chiefly on negative characters and on the vegetation rather than 

 the flora. A far more exhaustive botanical survey of the whole 

 area, especially west of the Tararua Ruahine Mountains, is 

 required and many local lists of species must be compiled, and 

 descriptions of the plant-associations writtten, before enough 

 material is available for comparative purposes. 



Coming now to the South Island, the southern boundary of 

 the Marlborough Sounds subdistrict is unsatisfactory. The 

 Wairau river forms the natural boundary between the forested 

 area of the north and the tussock-grassland of the south. But 

 here comes in a great difficulty. That is, what is to be done 

 with the high-mountain vegetation of the Dun Mountain and the 

 mountains drained by the R. Pelorus and the R. Wairau from 

 Mt. Patriarch eastwards. Their flora cannot possibly be united 

 with that of the Tararua Mountains, and it is not really a part 

 of that of the North-eastern Botanical District proper, neither 

 can it be united to the high-mountain flora of the North-western 

 Botanical District. On the other hand, the lowland flora, as 

 bounded by the Wairau River, might quite well come into the 

 Marlborough Sounds Subdistrict. This critical matter is one 

 for Nelson botanists to investigate, and its solution could well 

 be undertaken by the Cawthron Institute. The North-western 

 and North-eastern Botanical Districts are well-marked, as may 



