160 THE SALTON SEA. 



remaining 30 are usually found in places in which the concentration of the salts in the 

 soil-water is very low, and some of these are of xerophytic habit while others inhabit moist 

 areas. It is evident that the species which may be expected to appear in greatest number 

 on the beaches laid bare in the further recession of the lake will be drawn from the 17 

 pronounced halophytes; the presence of seepages and springs will afford small areas in 

 which others may appear. The secondary occupations or the species which might be 

 expected on the older and uppermost strands would be of the xerophytic trees, shrubs, 

 and herbaceous xerophytes. 



It is interesting to note that included among the earlier forms on the beaches was 

 Sonchus oleraceus, which was also one of the first plants to be found on the lava flows of 

 Mauna Loa, Hawaii, as observed by Forbes. 1 The seeds of this widely disseminated weed 

 are undoubtedly carried long distances, and as they are produced in great profusion may 

 be expected almost anywhere in the tropics or temperate zones. 



HISTORICAL. 



The strand flora of Krakatau included but 67 species in 1906, as reported by Ernst, 2 

 although the strand flora of the Indo-Malayan region comprises about 320 species. It is 

 thus to be seen that not one-fourth of the plants, the habits of which were suitable for 

 such conditions, had been carried to the shores of this island sterilized by volcanic action in 

 a quarter of a century. The total flora in 1906 included but 92 seed-plants and 22 ferns and 

 mosses. Ernst estimates that 39 to 72 per cent of these may have been brought to the 

 island by sea-currents, 10 to 19 per cent by birds, and 16 to 30 per cent by air-currents. 

 This author attributes the transportation of the 16 ferns to this last agency, also all of the 

 compositaceous species. 



Britton, in a recently published discussion of the derivation of the flora of Bermuda, 3 

 points out that 80 per cent of the higher plants are identical with forms native to the West 

 Indies and to the mainland of North America. The analysis of the habits and occurrence 

 of these species leads to the conclusion that 41 (or over 18 per cent, including all of the 

 halophytes) have been carried to Bermuda by flotation and 38 per cent by air-currents. 

 The grasses and compositse, as well as ferns and mosses, are supposed to have arrived in 

 this manner. 



The presence of nearly 44 per cent is attributed to birds. It is to be noted that the 

 island of Krakatau is separated from other land by only a few miles of open water, while 

 Bermuda lies far out in the Atlantic and nearly 600 miles of ocean separate its surface from 

 Cape Hatteras, the nearest land. It is also important to consider that the revegetation of 

 Krakatau has been in progress but a few years, while the carrying of seeds and spores to 

 Bermuda has gone on without interruption for an extremely long period. These differences 

 may well account for the much greater importance attached to birds as carriers in the case 

 of Bermuda and the lessened effectiveness of flotation. It is notable that these authors 

 estimate the part played by winds as practically the same. 



THE PHYSICAL CONDITIONS OF THE SALTON SINK. 



The general setting of the biological stage around and on the Salton is much different 

 from the complexes furnished by Bermuda or Krakatau. The islands in the Salton Lake 

 were submerged in salty water and emerged to pass by rapid desiccation to an arid condi- 

 tion. Their surfaces are separated from the mainland by distances nearly as great as 

 those of Krakatau, however. Fresh-water inle ts constantly pour currents laden with silt 



1 Preliminary observations concerning the plant invasion on some of the lava flows of Mauna Loa, Hawaii Occa- 

 1,°P 19?1912 ^ P Um ° f P ° lynesian Ethnology and Natural ffistory^ol. " No. 



* The new flora of the volcanic island of Krakatau, p. 57. Translated by A. C Seward 1912 

 3 Botanical explorations in Bermuda. Jour. N. Y. Bot. Garden, vol. xin, p. 1S9 1912.' 



