164 



The DISTEIBUTION of MAEINE ALG.E in SPACE 

 and in TIME. 



By George Murray, F.L.S. 



SENIOR ASSISTANT, BOTANICAL DEPARTMENT, BRITISH MUSEUM. 



At the outset it is necessary that I should expressly limit 

 and define the headings of this address. By the distribu- 

 tion of Algae in space, I mean not only their distribution 

 in natural areas of the waters of the globe, but also their 

 "vertical distribution" or "zonal distribution" or "range 

 in depth" as it is variously termed. Their distribution in 

 time is imperfectly ascertained by a study of their fossil 

 remains. Farther, I propose to limit the consideration 

 of the subject to Marine Algae or seaweeds, since so little 

 is known of the distribution of fresh water Algae, that he 

 would be a bold man who should venture to address you 

 on it. 



One of the first observations of general import made by 

 a student of Algae is that between tidemarks and beyond, 

 their occurrence is more or less regulated by their colour. 

 With certain notable exceptions the inshore Algae are 

 green, from half-tide mark olive and brown, mixed with, 

 and sheltering red, and lowest of all red. They do not 

 occur in definite zones since the red forms advance up- 

 wards under cover of the brown and olive forms, and, 

 moreover, there are exceptions for which I cannot account 

 on any theory. For example, to take extreme cases — a 

 brown fucoid, Pelvetia canalicidata, occurs at high water 

 mark, where it may be observed actually higher on the 

 rocks than certain maritime lichens ; and a green alga 



