294 THE BIOLOGY OF THE SEA-SHORE 



The advantage which this product offers as a culture medium 

 for bacteria is that it remains solid at a considerably higher 

 temperature than does gelatin of animal origin. It is also 

 quite free from impurities. 



Brown Seaweeds. — So far as this country is concerned, 

 the value of brown seaweeds lies in their manurial qualities, 

 although they are employed in all kinds of ways by the 

 Japanese, notably in the preparation of Kombu (from species 

 of Laminaria) which is much esteemed as an article of food. 



The use of seaweeds as manure is almost world-wide. 

 They are either cut direct from the rocks, or the masses 

 cast ashore after gales are collected and carried to the 

 adjacent fields, or carted inland as far as is convenient. 

 The species thus utilised are the various Fucoids : F. spiralis, 

 F. vesiculosus, F. serratm, and Ascophyllum nodosum, together 

 with Laminaria digitata and L. cloustoni, while at times 

 the non-algal Zoster a and others are employed. 



Seaweeds as manure contain about as much nitrogen 

 as farmyard manure (but in a form rather less available as 

 plant food), about half as much phosphates, and considerably 

 more potash, besides supplying a large amount of organic 

 matter. The following analyses are taken from the Ministry 

 of Agriculture leaflet No. 254 : 



