INTRODUCTION. 15 



disposed to become scientific blacksmiths, and to forge keys to the 

 treasures they have locked up in their formidable monographs. In- 

 deed, it is not possible that they should. They have no time to make 

 the entrance ways easy and agreeable. They are after the facts of 

 the science; they are seeking the internal secrets of the creatures 

 they have studied and written about; they are content to leave the en- 

 larging of the building to other specialists that may come after. It is 

 no fault of the writers of learned monographs that they put forth 

 their treatises without a single loop-hole of entrance for those that 

 would, if they could, enter in to see some of the treasures of which 

 rumor has told. When a man has spent his days and his nights and 

 his earthly and bodily substance on the production of a treatise that 

 shall make his name known to the world, he is naturally disin- 

 clined to labor longer and harder to make easy grades and smooth 

 paths and shady retreats along the way to his treasure house; and 

 when the learner has 'arrived at the gates, the learned man is not dis- 

 posed to stop his further investigations to throw a pretty key out of 

 the window and ask the uninvited guest to come m and sup with him. 

 He is too busily engaged in the new investigation that his completed 

 investigations have made necessary. There is no end to the questions 

 to be studied and decided. He cannot, much as he may be willing 

 condescend to make keys for the beginners. If he makes any at all, 

 they will be of the severest kind and intended for his scientific equals 

 only, not for the humble followers in his foot-steps. We should 

 never blame the writers of learned monographs for not offering these 

 gilded keys. They cannot. They have gone up too high to stop for 

 the higher they go the more there is to be done. And they that have 

 climbed that high are the ones best adapted to climb higher, for they 

 find it easier to go up than to come down. 



But if such books are to be used by any others than the rather 

 limited class of experts that have the knowledge needed to find their 

 way unaided through the pages, then a guide of some kind must be 

 furnished. An index will not answer the purpose, as to use it de- 

 mands just that information not at the disposal of the novice orof the 

 amateur. All of these scientific treatises may be as useful to the 

 modest student as to the learned investigator, provided, as I have so 

 often said and repeated, some means can be devised by which he 

 may be helped to make an intelligent entrance into its various depart- 

 ments. 



Mr. Wolle's monographs on the Algse and the Desmids are no 

 exception to the rule. They are not adapted to the use of the ama- 



