85 



do these cryptostomata occur in association with the 

 sporangia. In its case the cryptostomata are found 

 on the sporangium-bearing surface, though repeated 

 observations have failed to discover sporangia within 

 the cryptostomata. They stop at the brink of the 

 cavity, and indeed overhang it. 



The Geographical Distribution of the order is 

 throughout the temperate and polar seas, being 

 limited by the warm waters on the one hand and 

 the permanent ice on the other. Laminaria Schinzii 

 just enters the tropics at Walfisch Bay on the 

 south-west African coast, but within the influence of 

 a cold current. Laminaria and its immediate allies 

 are characteristic of the northern seas. Lessonia 

 inhabits the Pacific north and south, while Macrocystis 

 has an immense range in the southern seas, and in 

 the Pacific up the whole American coast to Alaska 

 and over to the coast of Asia at Kamtschatka. It 

 does not extend up either the African or South 

 American shores of the Atlantic to any extent. The 

 Pacific coast of North America, otherwise rich in 

 Laminariaceffi, possesses the peculiar genera Dictyo- 

 neuron, Postelsia, Nereocystis, Cymathwre, Pterygc- 

 phora, Egrcgia, and Eisenia, many of them limited 

 to California, and all of them with only one species 

 except Nereocystis. Alaska has thirty species, and 

 California, so rich in generic types, has fifteen, but 

 they have only three of them in common. Ecklonia 

 occurs in the southern seas and in Japan, while 

 the too numerous species of Alaria are all northern. 

 The genera occurring in the British seas are Lamin- 

 aria, Saccorhiza, Alaria, and Chorda. 



