INTRODUCTION. 13 



the plants that most of them may be identified without 

 its aid. 



Suffice it to say, that the whole class naturally 

 divides itself into three main groups, characterized in a 

 general way by their color, viz. : Red, Olive Green, and 

 Bright Green. These three groups correspond very 

 nearly to their more exact classification on the basis 

 named above. The lowest and simplest, in their organ- 

 ization, are the bright or grass green Algae, for example 

 the Ulva ; next the olive green, . the " Rockweed " 

 and " Kelp " ; the highest, the red Algae. I shall 

 take up each of these groups separately, and describe 

 the several genera and species, in their natural order, 

 following the arrangement adopted by Dr. Farlow, 

 from Prof. Thuret, in his list of North American Algae. 



TIMES AND PLACES FOR COLLECTING. 



Most collecting on our Atlantic coast, will be done 

 during the summer, and early autumn months. But 

 I must remind those of you, who live by the sea, or 

 have it accessible at all times, that many things of 

 the greatest interest and beauty, will be missed, if 

 you do not go to the shore early. Our finest Ca//i- 

 thamnion^ C. Americanum can be had in its rarest 

 beauty, early in March and even in February. The 

 finest varieties of our Rhodomela subfusca are only 



