INTRODUCTION. 17 



"finds," I shall feel that I have done some little thing to help them 

 and their friends. I shall feel pretty sure that the mere finding of 

 the name will not be the end; but if it should be, where will be the 

 harm ? Is it a crime to know the scientific name of the plant or of the 

 animal ? Knowing that is knowing something, I think. Would you 

 have the pupil dissect the nervous system before he has learned to 

 recognize a nerve, or before he knows the muscles to which the nerves 

 are distributed ? Of course he might say "This is a nerve," and "That 

 is a nerve and it goes to that muscle," but would you have him carry 

 the dead body about with him in order to dissect it and point out the 

 nerves and the muscles that receive them whenever he wished to com- 

 municate with you or with any of his friends in refere'nce to the nerves 

 and the muscles of that special creature ? This is exactly the result 

 which those that cry out against learning names would accomplish 

 if their desires prevailed. No, no ! Get the name the very first 

 thing, if you wish. It will make a good starting point. It is not the 

 end and the aim of any study; it is only the bridge that takes us over 

 the swamp. After awhile we will be big enough and strong enough 

 to pass the swamp without the bridge, as after awhile we will be able 

 to get along without an artificial key. But do not condemn the bridge 

 that has carried you safely over. 



The keys in this little book are as artificial as they could be made. 

 In some instances they are perforce somewhat natural; that is, the 

 fruiting plant has been used to the exclusion of the more frequent 

 sterile condition. This, however, has been avoided as much as possi- 

 ble, and in several instances two keys have been prepared to the same 

 genus of plants, one for the fertile, the other for the sterile filaments. 

 They are all, as the title page indicates, founded on the classification 

 contained in the admirable monographs by the Reverend Francis 

 Wolle on the fresh water Algae and the Desmids of this country. Un- 

 til Mr. Wolle took up the subject our American microscopic plants 

 had scarcely been touched, except by a few observers in a desultory 

 way. He has brought order out of chaos, and has prepared two mon- 

 ographs that are monuments to his learning, skill, care and patience. 

 These keys are made not alone with the object of leading the begin- 

 ner to the study of the fresh water Algae and the Desmids, but to in- 

 troduce him to these fine works of Mr. WoUe's. While the beginning 

 mcroscopist in his study of microscopical botany may, to a certain ex- 

 tent, succeed in identifying his "finds" with these keys alone, to do 

 so with entire satisfaction he should have access to the monographs 

 on the Algae and on the Desmids. The references at the end of the 



