MARINE BOTANY. <J 



tions. The olivaceous brown, or olive-green, is almost 

 entirely confined to marine species, and is, in the main, 

 characteristic of those that grow at half- tide level, becoming 

 less frequent towards low- water mark ; but it frequently 

 occurs also at greater depths, in which case it is very dark, 

 and passes to brown, or almost black. The red, also, is almost 

 exclusively marine, and reaches its maximum in deep water. 

 It is rarely very pure much within the range of extreme 

 low- water mark, higher than which many of the more deli- 

 cate species will not vegetate; and those that do exist, 

 degenerate in form as well as in colour, as they recede from 

 it. The green species are of the simplest structure. The 

 olivaceous are the most perfect and compound, and reach 

 the largest size ; and the red form a group distinguished no 

 less by the beauty and delicacy of their tissue, than by 

 producing seeds under two forms, thus possessing what is 

 called double fructification. 



In the wise economy of nature, the Algae are employed to 

 purify the waters, as plants purify the air ; they also serve 

 as food and shelter for various species of marine animals, 

 which in their turn become food for larger animals, and 

 for man. They are also employed for manure, for which 

 use they are, in many parts, and especially on the coasts of 

 Ireland, considered of the utmost importance. Some kinds 

 of Algae have been employed as food for man; others as 

 medicines ; and from one of the tribes kelp is obtained — an 

 article used in the manufacture of glass and soap. It is 

 probable that these vegetables are capable of being applied 

 to many useful purposes yet undiscovered ; and the study of 

 Marine Botany may tend to enhance their value. 



DIRECTIONS FOR COLLECTING AND LAYING OUT SEA-WEEDS. 



It must be borne in mind, that if exposed to the sun or 

 rain, the plants, as a general rule, soon change colour. The 

 gleaner should, therefore, always seek for them at low tide, 



