136 Transactions. 



is tallest. In tke greater part of the swamp the following appear to be signs 

 of drying up : Typha angustifolia is of small size ; Juncus effusus is abundant ; 

 various other plants, such as Mariscus ustulatus, Ageratum conyzoides, and 

 Poly podium diver si folium, are appearing ; and, finally, plants of Metrosideros 

 villosa up to 2 m. in height occur in various places, chiefly on the higher 

 ground, where water does not actually lie on the surface. The cause of this 

 change is probably the filling-in of the swamp by material washed into it 

 by rains. 



The swamp surrounding the Blue Lake is similar to that in Denham 

 Bay, but contains fewer species of plants. Besides Typha angustifolia, 

 Mariscus ustulatus and Paspahim scrobiculatum are the chief plants. This 

 swamp is of recent origin, as the water in the Blue Lake was probably boiling 

 during the eruption of 1872, there being a number of standing dead trees 

 near its shores. 



(c.) Lakes. — From the edge of the Green Lake the bottom slopes steeply 

 into deep water. In places, however, there is a shelf just submerged, and 

 here Typha angustifolia finds a foothold ; but in all cases there is a space 

 of about a metre between it and the water's edge, this being the distance 

 goats are able to reach when standing in shallow water. 



Tui Lake is a small sheet of fresh water surrounded by forest, and Ues 

 on the edge of the area afiected by the eruption of 1872. A little Typha 

 angustifolia occurs, and Callitriche Muelleri grows either entirely submerged 

 or on the bank close to the water's edge. 



■■to^ 



3. Forest Foi'mations. 



(a.) General Remarks. — Practically the whole of Sunday Island is covered 

 with forest, this being the true climatic plant formation. The proportion 

 of ground occupied by other formations would be insignificant when com- 

 pared to that under forest, which reaches from the water's edge to the tops 

 of the highest hills, were it not for certain disturbing influences which may 

 be termed accidental, and which have led to the existence of the plant forma- 

 tions described below as " young " and " introduced." But cUmate, being 

 a permanent unchanging factor, must in the long-run overcome any tem- 

 porary disturbing influences, and consequently forest will gradually replace 

 the new formations. This process is certainly going on with regard to the 

 young formations, which might appropriately be called young forests ; 

 but the occupation of man, which is responsible for the existence of the 

 introduced formations, may become a permanent factor ever preventing 

 the forest regaining its lost ground. I have already mentioned the change 

 which is apparently taking place in the swamp in Denham Bay ; but this 

 is a slow, natural process consequent on the filling-in of the swamp by 

 material washed into it by rains, and, possibly, the gradual upheaval of 

 the Kermadec Islands plateau. 



Though small, Sunday Island is hilly in the character of its surface, and 

 a considerable area is over 300 m. above sea-level ; hence the amount of 

 atmospheric precipitation is not the same in all parts, and consequently the 

 character of the forest varies. The soil is everywhere extremely permeable, 

 so that it may be disregarded as a factor determining the distribution of 

 the main types of forest. The more elevated parts of the island undoubtedly 

 receive a much greater amount of moisture than the lower parts. In 

 northerly weather everywhere above an altitude of about 300 m. is enve- 

 loped in clouds, while the lower ground receives moisture only while it is 



