l6 INTRODUCTION. 



teur microscopist in the state in which the author has left them. It 

 is not possible for the youthful microscopist to read the description 

 of one hundred and twenty genera of Algae in order to locate a 

 single specimen that he may find in the wayside ditch. To ascertain 

 with any degree of comfort the probable resting place of the speci- 

 men he must have some help. It is that help that this little compila- 

 tion hopes to supply. By its intelligent use the student may ascer- 

 tain the specific name of any fresh water Alga or Desmid in the ponds 

 and the ditches of the United States. This he can do with the ex- 

 penditure of the least time and labor, leaving them to be spent in the 

 subsequent study of the plant, after he has had the satisfaction to 

 learn what it is, and where in the classification it belongs. If the 

 worker has the name of the specimen, he then feels that he has a sup- 

 port on which he may hang his subsequent information, and a starting 

 point for further investigations. Not to know the name of the ob- 

 ject and yet to try to study it, is like an attempted conversation with 

 a stranger whose antecedents and local habitation are unknown. 

 The effort is not an agreeable one. The conversation languishes, and 

 interest is lacking. The name and the habitat of the person add 

 much to the pleasure of the meeting, and many suggestions to the in- 

 terview. So the name of the microscopical or other specimen is al- 

 most essential to the well being of the young student. 



The name is, too, about the first thing the advanced scientist tries 

 to learn. It is impossible to do otherwise. The object can not be re- 

 ferred to by speech or in writing until its name is known; what other 

 workers in other parts of the world may have said about it or done 

 with it, can not be known until its name is learned, as without the name 

 all indexes are closed in all the books of all the libraries. The name 

 is the clue to further knowledge, its starting point, even the hook upon 

 which further information is to be hung. Whatever advanced scien- 

 tists may say to the contrary, their first effort, perhaps it is an uncon- 

 scious one, but their first real effort is to ascertain the name of their 

 new specimen. If it has none, they at once proceed to give it one. 

 All the wild talk about the undesirability of learning the name is 

 wrong in principle. The name is, as every one will cheerfully admit, 

 only of secondary importance when compared with a study of habits 

 or of morphology, but it is as essential, since it is and must ever be 

 the starting point for further investigations, at least on the part of the 

 amateur. If he chooses to stop at the name, that is his misfortune; 

 but even then he has gained something. If those whom I may be able 

 to help by these keys shall do nothing more than identify their 



