XIV DESMIDS OF THE UNITED STATES. 



results, since the drying is apt to collapse, or otherwise distort 

 the cells. 



The collector will not know the value of his find, until it has 

 been brought drop by drop under the lens of his microscope, and 

 out of the entire mass he may discover nothing to reward his 

 labors ; this however should not discourage him, as one or two 

 failures are to be expected prior to meeting with an adequate 

 reward. His interest in the study will be greatly enhanced if 

 he keeps a record of it in sketches of what the microscope reveals 

 to him. These sketches should, of course, be very exact, and in 

 order that they may be so, it is necessary that the microscope 

 should be provided with an eye-piece micrometer with which to 

 measure the length and breadth of the figure to be sketched ; a 

 half inch per ytfW (.001") or 25 n is the most convenient, though 

 i or i of an inch may be a preferable scale for the larger forms. 

 It is so difficult to separate specimens from their accompanying 

 foreign matter, that it is seldom amateurs can mount them sati> 

 factorily on slides, and therefore this method of preserving 

 specimens is not open to recommendation. 



Although in the microscopic study of the fresh-water Algce 

 much has been done within the past few years, much more re- 

 mains to fte accomplished. The field, instead of growing smaller, 

 seems to widen out with every fresh discovery ; localities thought 

 to have been exhausted of additional possibilities, have in sub- 

 sequent seasons, yielded ample returns to the patient explorer ; 

 and if the old territory is not sufficiently attractive, there are 

 vast regions into which no student has yet penetrated, where, 

 doubtless, the harvest awaiting the reaper dwarfs all that has 

 been heretofore garnered. 



