126 THE SALTON SEA. 



on the beaches. Heliotropium curassavicum was abundant in many places on the strand. 

 Sphceralcea orcuttii was represented by a single individual, part of which was preserved. 

 Lippia nudiflora occupied a position immediately below the high flood level. Prosopis 

 pubescens, two individuals, and one P. glandulosa arose from a living branch which had 

 been carried to the southeastern point of the island and cast ashore, after which it had 

 been half buried in the sand. 



The entire southeastern shore of the island was exposed to the direct action of the 

 water which was being emptied into the lake by the Alamo and New Rivers. The feeble 

 current of these streams would be an agency of slight efficiency in carrying plants across 

 the intervening 7 or 8 miles of open water, but once branches or seeds were afloat on the 

 waters of the lake, wave-action might bring many of them ashore on this island. Oligomeris 

 glaucescens was the most abundant of the invaders. Parosela emoryi was represented by a 

 few plantlets on the sorted beach ridge on the shore of West Bay. As will be shown later, 

 this is a species which appears on gravelly shores immediately following the recession of the 

 water and apparently maintains its place in the rank during hundreds of years of aridity. 

 Typha was found at the high flood-level on the eastern shore, evidently arising from a 

 rhizome. Baccharis glutinosa had found lodgment in the mud of West Bay, apparently 

 from floating seeds, and Leptochloa imbricata was established near the high level of the 

 flood on West Bay. The examination of this place in February 1908 completed the initial 

 examination of the observation areas and furnished a census of the pioneer introductions. 

 The fate of the original introductions, together with the accession of additional species, now 

 constituted a subject which aroused keen interest on the part of the workers engaged. 



The next visit to Obsidian Island was made on May 8, or only three months later. 

 The multiplication of the fish which had come into the lake with the water from the Colo- 

 rado River had made a supply of food for aquatic birds, while the elevated arid summits 

 of this and other islands uninhabited by any carnivorous animals had attracted large 

 numbers of pelicans and cormorants which had occupied areas of several acres in extent 

 with nests constructed among the rocks and desert vegetation. Many of the plants were 

 destroyed, while the continuous trampling on the dry soil offered but slight opportunities 

 for any introduced seed to give rise to a plant that might reach maturity. 



Nothing had as yet appeared on the part of the beach laid bare by the recession of 

 1908, but the opportunity was good for observation on the condition of the invaders which 

 had been seen three months earlier. Oligomeris glaucescens, Eriogonum thomassii, Sonchus 

 asper, Cryptanthe barbigera, Psathyrotes ramosissima, Cucurbita palmata, Lippia nudiflora, 

 Rumex berlandieri, Aster spinosus, and Pluchea sericea were maturing seeds and thus furnishing 

 material for reproduction of the pioneers. Distichlis spicata and Leptochloa imbricata were 

 also found. Atriplex canescens and A.fasciculata had maintained themselves on the beach, 

 while A. linearis and A. polycarpa were not to be found. The two young trees of Prosopis 

 pubescens and one of P. glandulosa were thriving. Oenothera, Encelia, and Sphceralcea had 

 apparently disappeared, while Heliotropium was represented only by dead stems and prob- 

 ably a crop of seeds on the ground. It might therefore be said that the change in the 

 population included one addition, that of Aster spinosus, and three losses. 



t ?t • Sl i 0re °f the entire northern end of the isl and was rocky and afforded no lodgment 

 tor the higher plants. These were confined to a strip running from East Bay to a point 

 midway of the southern end and to the shore of West Bay. All of these places were sub- 

 ject to heavy storms, so that strands which had been long above the level of the quiet 

 water were subject to the wave-action of the water, which had by this time taken on a con- 

 centration of 460 parts in 100,000. The shores of sand, clayey material, and heavy gravel 

 were steep and the terracing could not be so definitely assigned to any season with cer- 

 tainty, since storms might entirely obscure the effects of a water-level which had remained 

 stationary for some time earlier in the year. 



