118 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 3 



very near to the end of one. Beach-drift specimens at the same time must 

 be considered separately, for it seems that the suspended state may prolong 

 the life of such plants after they have left the original habitat, and thus 

 create an overlap in the cycle whereby one generation continues to linger 

 as a floater, while the succeeding one proceeds in its development. 



Aside from the interesting changes in the Sargassmn vegetation of 

 Turner's Island as observed at the two seasonal extremes, there were 

 other changes of an equally pronounced nature. In January about fifty 

 species were collected on the reef, and in July about the same number was 

 found. However, the expression of the flora of the reef was strikingly 

 different at the two seasons. During the winter, Colpomenia had been 

 dominant over a great part of the cobble shore, associated with an abun- 

 dance of Padina and Codiui?i. All of these were gone by summer, together 

 with Gigartina, the greater part of the jointed corallines, and many small 

 rock-cover types. Over everything grew clumps of Dictyota, a large 

 species six to ten inches high, forming the great bulk of the plant life. 

 Some species which had been encountered in mature stages in January 

 were recognizable in July in their juvenile stages, but others were appar- 

 ently absent or greatly reduced in number. 



It seems certain that this great change is due primarily to the widely 

 contrasting seasonal temperature relations. A comparison with the situa- 

 tion on our California coast reveals no such temperature extremes. In 

 January the open sea at Turner's Island measured between 60 and 64 

 degrees F., while in July this same water had warmed to 88 degrees. 

 Insolation in the summer is exceedingly severe and, no doubt, produces 

 much higher temperatures on the surfaces of exposed plants at low tide 

 and in small pools. On Tiburon Island, in the bays along the shore, 

 temperature figures as high as 92 were common. 



Some mention may be made of the deepwater collections secured by 

 the Hancock Expedition, since they far exceed all previous ones from the 

 region. The immediately sublittoral dredging yielded a great number of 

 species not found in any of the shore stations; indeed, the hauls from 6-16 

 fathom depths were among the most productive collections made. In 

 deeper water, 11-22 fathom.s, a number of genera of membranaceous red 

 algae were secured, and even in a 30-40 fathom haul several species came 

 up, though it was suspected that a part of these may have been detached 

 pieces from lesser depths. Conspicuous among the deepwater specimens 

 were certain crustaceous corallines which were usually the only represen- 

 tatives of the plant kingdom. On the Gorda Banks off the Cape of Baja 



