vi INTRODUCTION. 



American botanical laboratories previous to that time, and even in 

 Germany it was but little in vogue. To study better methods of 

 microscopic manipulation in this and other directions, was the 

 object of the writer in spending the year 1887-'88 in the German 

 laboratories, where he used for the first time the collodion method 

 of imbedding. It was seen more and more clearly that in the 

 future, students were to be trained to useful work in biological 

 investigation chiefly through a mastery of microscopical technique, 

 and a thorough knowledge of tissues and cell contents with their 

 behavior under the influence of reagents. The changes in methods 

 in the histological course brought about during the four years 

 following 1888, were made to bear upon the work of students taking 

 the courses on the higher and lower Cryptogams, with most excel- 

 lent results. Such changes were included in the plans for a revised 

 manual, carefully drawn up in 1892. 



Mr. Mason B. Thomas, an undergraduate, then Fellow in 

 Botany in the writer's laboratory, 1888-91, and afterward Profes- 

 of Biology in Wabash College, was invited to assist in this work. 

 During his university course he had been able to render me invalu- 

 able assistance, by refining and abridging the process of imbedding 

 in collodion, and by devising various laboratory appliances con- 

 nected with it (still remaining in the laboratory at Cornell), some 

 of which are described in his papers published in 1891 to 93, * and 

 detailed at some length in Atkinson's " Biology of Ferns" (1894), 

 particularly in Part II., Chapter I. 



The exactions of work since 1892, in an entirely new field have 

 obliged me to abandon rewriting the Manual. At my request, 

 Professor Thomas has done this, so far as it seemed necessai'y. 

 He has also prepared the part on technique (Part I.), as well as 

 plates, selecting the illustrations from his many beautiful prepara- 

 tions made while at Cornell University and since that time. The 

 fact that some of the best laboratories in this country have adopted 

 the methods formulated by him makes it particularly appropriate 

 that he should write this part. 



In it no attempt has been made at an exhaustive treatise but 



* (1) "The Collodion Met hod in lot;in v :" Hep. AIM. Society of Micnxcopists, 

 1891; (Mi "A Dehydrating App.-n-itu-,." A.m. Monthly Microscopical Jol., Jan., 1H91. 

 (3) "Sectioning Fern Prothaflla," The Microscope, SOT. 1893. 



