108 PLANTS, SEEDS, AND CURRENTS 



in giving relief to the submerged region, and the people of the neigh- 

 bourhood then dig a trench through the beach for carrying off the 

 surplus water. 



It is therefore evident that the hydrographical features of the 

 district of the Salt Lakes vary greatly in different seasons. Although 

 the drainage of the waters from the Great Morass is relatively small 

 for most of the year, it is large in the wet months. After the rains 

 the lagoons are greatly increased in size and their water is nearly 

 fresh. During the dry months they shrink considerably and become 

 very salt, the smaller lagoons being sometimes completely desiccated 

 or reduced to scanty lakelets only a few inches deep. This alterna- 

 tion between a state of high salinity and a condition when the water 

 is almost fresh must have an influence on the distribution of the 

 vegetation. 



When I visited this locality in the middle of January intermediate 

 conditions prevailed, such as exist probably through the greater half 

 of the year. Some of the lesser lagoons had dried up, being repre- 

 sented by expanses of white mud. Others were reduced to ponds a 

 few inches deep, the water being very warm and very salt. In the 

 case of a greatly shrunken lagoon nearest to Paroti Point, the density 

 and temperature of the water at midday were respectively 1*031 and 

 88° F., the values for the sea at the same time being 1*026 and 79° F. 

 In the larger and deeper lagoons the contrast between their salinity 

 and that of the sea was slight. Under similar conditions of tempera- 

 ture the salinity of the water was 1*028 and that of the sea 1*026. 

 At first sight the Salt Lakes district would appear to be well fitted 

 for the salt-pan industry, but the fresh- water from the great inland 

 swamps, especially after the rains, would probably prevent the 

 success of such an undertaking. 



General Character of the Vegetation of the Salt Lakes 

 District. — Avicennias among the trees and Salicornias amongst the 

 lesser plants form the predominant features of the vegetation occupy- 

 ing the extensive expanses of white mud that give the character to 

 the district of the Salt Lakes. Then come the mangroves at the 

 borders of the larger lagoons, and here the same Avicennia (A. 

 nitida) takes its place with Rhizophora mangle and Laguncularia 

 racemosa in the swamp. Around the shores of the Great Salt Lake 

 the Rhizophoras and the Avicennias are, however, the most frequent, 

 sometimes the one, sometimes the other, usurping the lake's margins. 

 All three mangroves thrive in the creek which leads from the beach 

 to the lake. In the smaller lagoons, where the water has been 

 reduced to a depth of a few inches and has a greater salinity, the 

 Rhizophoras disappear from the mangrove belt, leaving the Avicen- 

 nias and Laguncularias in possession of the borders of the partially 

 desiccated lake. On the expanse of exposed mud-flats Salicornias 

 and Batis maritima thrive. When the water has evaporated away 

 and only a shallow depression indicates the original lagoon, the 

 Laguncularias in their turn disappear, and Avicennias with Salicornias 

 and Batis maritima alone remain. 



Avicennias grow in this district under all the various soil-conditions 

 that are presented, whether in the salt-water swamp, in the wet salt 



