16 PRACTICAL BOTANY. 



It is often desirable to observe objects in the living 

 state for a considerable time under the microscope. This 

 must be done in a moist chamber. A moist chamber 

 may be readily constructed as follows : A piece of thick 

 rough cardboard is cut to the size of the glass slide, and 

 a circular hole is punched out of the middle of it of 

 such a size as to be covered by a cover-slip. The piece 

 of cardboard is then soaked in water (or boiled in water 

 when pure cultures of Fungi are to be made), so as to 

 saturate it, and placed on the glass slide. A drop of 

 water (or solution as described below), is placed on the 

 cover-slip, the object is immersed in it, and the cover- 

 slip is then inverted over the hole in the piece of card- 

 board. Thus the object is suspended in a drop of liquid 

 on the under surface of the cover-slip. Any loss from 

 the chamber by evaporation is prevented by occasion- 

 ally wetting the cardboard on the slide. 



The liquid to be used will of course vary with the 

 nature of the object to be observed. In the case of 

 AlgaB, water may be used ; in the case of Fungi, decoc- 

 tions of various organic substances (fruits, animal 

 tissues, &c.), or a solution of sugar, according to the 

 habit of the Fungus. For observing the germination of 

 the spores of Mosses and Ferns, water will suffice ; but 

 in the case of pollen-grains a solution of sugar is neces- 

 sary (1 20 or even 30 per cent, the concentration 

 being different for different plants) ; for observing the 

 process of cell-division in the hairs on the stamens of 

 Tradescantia, a 1 per cent, sugar solution may be used. 



