Chapter V. 



Brown Algae and Red Algae. 



Brown algae. Almost all of the true brown algae are marine 

 and they are remarkable as comprising the longest plants in the 

 world. It is a popular impression that the big-trees of Cali- 

 fornia, the Eucalypti of Australia and the Rotang palms of Java 

 and the Orient are the longest-stemmed plants in existence. 

 This, however, is a mistake for some of the gigantic seaweeds 

 of the Antartic ocean extend their stems for over a thousand 

 feet, making them nearly three times as long as the trunk of the 

 tallest big-tree in Calaveras county, California. Such huge brown 

 algae are not unknown along the sea-coast of the United States, 

 and the giant kelp of Puget sound sometimes reaches a length 

 of more than three hundred feet. By means of its long cable- 

 like axis, it attaches itself to the rocks and floats its immense 

 leaves many fathoms out upon the surface of the sea. Other 

 brown sea-weeds develop enormous strap-shaped leaves in tufts, 

 attached by hold-fasts to the rocks. Some of them have their 

 leaves perforated with numerous holes, an adaptation to prevent 

 them from being torn by the waves. In the fresh waters of Min- 

 nesota no such forms as these are to be found and the most 

 abundant ones are doubtfully to be classed as brown algae at all, 

 but from their brownish or olive-green color they may here be 

 considered as if certainly members of the group. 



Diatoms. In the early spring, in rivers, one often finds olive- 

 green membranous masses as large as one's closed fist floating 

 idly at the water's edge. An examination of them would show 

 that they consist of great numbers of microscopic boat-shaped 

 bodies, with clear glassy w^alls and olive-green or browai con- 

 tents. Such algae are known as diatoms. They sometimes 

 occur in great fossil deposits, and in this condition are much 

 prized for polishing powder. The walls of the diatom cells 



