NO. 7 DAWSON : ALGAE OF THE GULF OF CALIFORNIA 117 



to revisit, in July, one of the richest algal habitats known there, the reef 

 at Turner's Island. Without the Velero III at this time marine collecting 

 in Mexico from a land approach presented quite a different problem. 



Bahia Kino is a broad baj^ of almost continuous beach. For a marine 

 botanist it yields little to excite enthusiasm, but on this occasion it con- 

 tributed to one problem in particular, that of the development of Sargas- 

 sum in the Gulf. 



The first Sargassum material found in fresh, wet condition on the 

 beach at Kino Bay could easily be separated into two foiTns. Both had 

 been capable of continued life and growth while floating and drifting in 

 the open sea. One clearly gave evidence of morphological modification 

 under these free-floating conditions ; the other, less strikingly. 



Sargassum was again encountered on the south of Tiburon Island, 

 where a species approaching fertility was found to be abundant on a 

 cobble shore, attached firmly to rocks by broad, discoid holdfasts. 



On Turner's Island, where in January great masses of Sargassum 3-6 

 feet long covered large areas of the lower littoral shore, a striking change 

 had taken place. These had all disappeared, and there remained only occa- 

 sional remnants of disintegrating fronds, below which were numerous 

 young shoots springing from the spreading holdfast region and just 

 beginning a new season's development. Two species of young Sargassum 

 were found, both in about the same stage of development and indicating 

 that a complete seasonal cycle occurs annually at that locality. In one of 

 these, destruction of the mature plants is accomplished most probably by 

 gradual disintegration in accordance with increasing water temperatures. 

 The other seemed to be one which breaks off to take on the floating habit. 

 These detached pieces may live and grow actively for a considerable time 

 before being cast up on the beaches, where they are destroyed by myriads 

 of beach isopods which consume them completely at each low-tide period. 



The obsei'vations thus far have shown the Sargassum flora to be 

 largely annual in development, either entirely from sporelings or from 

 perennial bases. However, the various species follow through their devel- 

 opmental cycles in different seasonal order. Thus, in January at Guaymas 

 two species were in full reproductive condition ; at Tepoca Bay to the 

 north another species had reached only the earlier stages, and maturity 

 was not due for some months. The same conditions were found to the 

 south at Agua Verde Bay, though the stages were still younger at that 

 time. In July, on the other hand, Turner's Island specimens were just 

 beginning a new cycle, and those on the south of Tiburon Island were 



