150 



without the inconvenience of nose-pieces and readjustment. A fixed camera 

 was a great advantage, so that a drawing or rough sketch could be made at 

 once. Sketches strongly recommeuded, and taking measurements accu- 

 rately either by means of an eyepiece micrometer, or a camera lucida sketch 

 of known proportions. 



V. Determination. — In order to determine the names of collected Algae 

 no royal l'oad could be indicated. The only method, safe and sure, was by 

 a scientific process, and not empirically. The fructification by all means 

 essential. The genus must be determined, through the fructification, com- 

 bined with the vegetative characters, and after that there would be com- 

 paratively little difficulty, with the aid of a manual. The great difficulty 

 usually was occasioned by the imperfect condition of the specimens. Re- 

 agents often useful in very hyaline objects before the outline can be dis- 

 tinctly made out. The aniline dyes readily available for this purpose. 



VI. Preservation. — Two kinds of preparation in vogue, the preservation 

 of portions for the microscope, and the preservation of entire plants for the 

 herbarium. Thin filaments of mica, most to be commended for preserving 

 the more minute species for the herbarium. Large filamentous algee to be 

 washed clean and floated out on squares of paper and dried, in the manner 

 adopted for marine algse. The majority of species are gelatinous enough 

 to adhere of themselves to the paper when dry. For microscopic prepara- 

 tions the chief difficulty is the fluid medium. Too dense a medium will at 

 once cause the endochrome to collapse, and the cell-walls to be distorted. 

 Most persons are content with the water in which the specimens were grow- 

 ing, with just a tinge of creosote. He had seen specimens mounted in this 

 manner, after twelve years in the cabinet, as fresh-looking as though col- 

 lected the day previously. Calcium chloride has also been recommended, 

 and in many cases, where no green colour has to be kept, may be used with 

 advantage. Glycerine, by its density, distorts most forms of Alga3. In all 

 cases mounted Algse must not be exposed to the light of day, or the colour 

 will vanish. 



VII. Cultivation. — These organisms are most interesting for cultivation. 

 Small aquaria may be extemporized of glass tumblers, placed at different 

 elevations. Connected to each other by thinly twisted cotton threads as 

 syphons, a constant change of water can be kept up from the highest to the 

 lowest tumbler, and the whole life-history of species watched at home. 

 Growing slides of various forms have been devised, each with some special 

 advantage. Terrestrial species will for a long time retain their freshness 

 on damp sand or wet flannel, under small bell glasses or inverted tumblers. 

 No objects in the whole round of animated nature are so capable of being 

 placed in natural conditions, and submitting to artificial cultivation. 



The implements and instruments necessary were exhibited, and alluded 

 to in conjunction with their application in the above sections. 

 The following objects were exhibited in the Library : — 



Difflugia pyriformis Mr. F. W. Andrew. 



T. S. Whisker of Cat Mr. E. C. Bousfield. 



Isinglass, polarized... ^ r « A. L. Corbett. 



Podophyra, sp Mr. C. J. Dunning. 



