RATE OF DEVELOPMENT OF INDIVIDUAL SPORES 45 



fogged just above the gill, owing to condensation of water vapour 

 upon it. In order to clear the fog away, it was necessary to remove 

 the top of the cell for a few seconds until the condensed moisture 

 had evaporated or to leave the cover-glass in position and to warm 

 it gently from above with a finger or heated needle. To avoid 

 fogging altogether or reduce it to a minimum, it was found advisable 

 to use diffused daylight re- 

 flected with the plane mirror 

 and to have the cover-glass 

 well raised above the gill under 

 observation. 



For Collybia velutipes.(Fig. 

 15), where the time of obser- 

 vation was only three-quarters 

 of an hour, the gill was rested 

 on a drop of water on an 

 ordinary slide. Owing to the 

 weather conditions being very 

 damp and the air in conse- 

 quence being almost saturated 

 with water vapour, it was not 

 even necessary to cover the 

 gill with a cover-glass : the 

 spores developed quite nor- 

 mally when the hymenium 

 was directly exposed to the 

 high objective. For Marasmius oreades a similar preparation was 

 made with the exception that a cover-glass was laid over the gill. 

 Here again, the development of the spores was very rapid (just 

 over an hour), and the air was very moist. Where, however, as in 

 Stropharia semiglobata, spore-development takes some hours, the com- 

 pressor cell is indispensable for keeping the gill continuously moist. 



The observations on Panaeolus campanulatus were made with 

 a horizontal microscope under conditions which will be described 

 in Chapter X. 1 For Coprinus sterquilinus individual spores were 



FIG. 14. A compressor cell used for 

 observing the development and dis- 

 charge of spores on the hymenium 

 of Hymenomycetes. A, viewed from 

 above ; g, a gill of an Agaric ; d, a 

 water-drop. B, vertical section ; b, 

 the glass base of the cell ; c, the 

 cover-glass ; ch, the moist chamber ; 

 g, a gill ; d, a water-drop. The 

 frame -work of the cell was made 

 of brass. The chamber, ch, can be 

 made larger or smaller by raising 

 or lowering the cap of the cell. 

 Actual size. 



1 Chapter X, section : " Apparatus and Method for Observing the Development 

 of the Hvmennim." 



