170 MOSSES AND LIVERWORTS 



plant, to show the nature of its growth, together 

 with one or two capsules ; the other, some leaves 

 (including a few perichoetial leaves"), and also a 

 portion of the capsule mouth, to give the peri- 

 stome teeth, and sometimes a piece of the capsule 

 wall showing the stomata. 



One word of caution on a small point may be 

 here given, and it will serve to emphasise the 

 need for care and cleanliness even in the most 

 trifling details. It is well, from time to time, 

 to clean out the small glass pipette used for 

 conveying the jelly from the hottle to the glass 

 slip ; this may be done by means of a very small 

 piece of sponge tied to the end of a thin strip of 

 wood. I remember being much troubled by the 

 constant appearance of a great number of minute 

 bubbles in the glycerine jelly, which proved to be 

 due to the fact that my pipette had been washed 

 in water which contained some admixture of 

 earthy matter ; this had formed a thin film inside 

 the pipette, and some acid quality in the jelly 

 evidently combined with an alkaline substance in 

 this earthy film to form carbonic acid, and so 

 caused the bubbles. In addition to occasionally 

 cleaning the pipette, I always dip it, after 

 finishing a mount, in acetic acid, and also, just 

 before using it again, rinse it out with alcohol. 

 Another small precaution that will still further 

 help to exclude these minute air-bubbles is this. 

 When putting the pipette into the bottle of melted 



