418 SEA-WEED COLLECTING. 



salt the dried specimens must be plunged quickh' into fresh 

 water and again dried between blotting paper. It can then 

 be added to the collection. How beautiful the specimens of 

 such a collection are, and how well they preser\'e their struc- 

 ture and colour mav be seen from the illustrations of ^^ ilo- 

 ph yllumpuiictatuni (Fig. p. 307) and Dc-lcsseria Ilypoglossuui 

 (Fig. p. l'>9), which were drawn from dried specimens. 

 If a bowl of sea-water containing Algae be shaken 

 in the dark, small flashes of light will be seen in it. This 

 is caused b\' luminous creatures which rest on the Algae 

 and emit sparks when disturbed. The Algae themselves 

 do not phosphoresce, but many of them have a curious 

 sheen in daylight and a wonderful brightness due to 

 reflection. Certain cell-contents of these Algae are so 

 constituted and disposed that the\' act like concave mirrors. 

 In the Mediterranean the finest effects are to be seen in the 

 genus (jJiylochuhci, Rhodoph\'ceae witli whorled branches, 

 which shine blue, silver\--white or pink, and are sometimes 

 iridescent. The brown Ccslosira also displays mauA' colours 

 when the waves move it to and fro in the sunshine. 



CHAPTER XII. 



A ver\' strong Mistral, that generally set in to\^•a^ds 

 midday, kept the sk)' clear, and we reached the second 

 half of April without rain. On the 20 th the sun sank 

 behind the Esterel in a clear sk^', but higher in the 

 heavens long streaks of cloud had gathered. Soon they 

 were tinged with red, and, imparting their colour to 

 Golfe Jouan, made the crested \vaves quite rosv. The 

 sky in the west, beyond the mountains, turned a deep 



