272 Transactions. — Botany. 



resist the action of waves can exist. In consequence the 

 lagoons of Chatham Island possess only a very small pha- 

 nerogamic flora; nor so far as observed were Alga numerous. 

 Ruppia maritima often occupies large portions of such shallow 

 places in lagoons, and its leaves and stems, floating at times on 

 the surface of the water, form a mat of such density as to have 

 attracted the attention of the Maoris, who call it the " eels' 

 blanket." The floor of the lagoons consists of sand or of 

 sandy peaty mud, formed from the decay of many generations 

 of plants. Such muddy peat is the commencement of a 

 transition from the bed of a lagoon to salt meadow, for as it 

 gradually accumulates it rises out of the water and becomes 

 at once occupied by an abundant plant population. Such a 

 spot forms the line of tension between lagoon and salt 

 meadow. In several places Te Whanga Lagoon is, as before 

 pointed out, sufficiently shallow to be crossed on horseback, 

 the depth of water at the crossing varying according to the 

 direction of the wind ; and with a north-west wind blowing in 

 summer it may be quite dry, and clouds of dust and sand 

 mark its position. On this portion of the lagoon-bed large 

 round patches of Samolus repens are abundant; so here is one 

 of the most characteristic of salt-meadow plants taking pos- 

 session of the ground almost before the station is fit to receive 

 it. A very slight rise indeed of the land and the bed of the 

 lagoon would be transformed by nature into salt meadow, 

 which probably might be succeeded by forest, especially if the 

 land were elevated a little more. It is also easily conceivable 

 how such a lagoon could be transformed into a bog, and it 

 seems very probable indeed that the low-lying boggy ground 

 in the north-west of the island has had this origin, as 

 suggested by Haast (23). 



Lagoon-shore. 



The vegetation of the lagoon-shore, as shown above, is not 

 directly related to that of the sea-shore proper, but is rather 

 an embryonic salt meadow. Of course, originally, before the 

 lagoon was cut off from the ocean, it must have been true 

 sea-shore, though possibly its plants might even then have 

 been affected by the lime in the soil. 



I had only an opportunity of examining a portion of the 

 western shore in one or two places, and have no notes at 

 all regarding the eastern shore. The soil consists of sandy 

 peat usually very wet, but varying considerably in its water- 

 content. That portion within reach of the wash of the waves 

 is sopping wet, and so soft that one cannot tread on it with- 

 out sinking halfway to one's knees. There Grantzia lineata 

 grows most luxuriantly, forming large green masses. Calli- 

 tricJie muelleri, Limosella aquatica, var. tenuifolia, Cotula 



