THE MECHANISM OF SPORE-DISCHARGE 149 



soon as they have settled on glass immediately after leaving the 

 basidia. 1 



For the purpose of finding out the mechanism of spore- 

 discharge, a transverse section through the hymenial tubes of 

 Polyporus squamosus was cut, and the horizontal basidia looked 

 down upon with the vertical microscope as already described for 

 Methods I. and V. 2 A particular basidium, bearing four ap- 

 parently ripe spores, was carefully focussed. After a watch had 

 been kept for some time, one of the spores suddenly disappeared. 

 The end of the sterigma left vacant was then seen to be pointed and 

 entirety devoid of any drop of fluid (cf. Fig. 53, p. 146 ; also Plate I., 

 Fig. 3, and Plate III., Fig. 16). The vacant sterigma also appeared 

 <x> be quite as long and as turgid as the other three still bearing 

 spores. The basidium did not seem to have altered in volume. 

 There was nothing to suggest that the sterigma had opened and 

 discharged a mass of fluid through its very fine neck. The end 

 of the sterigma, which is only about 0'5 p wide, gave the im- 

 pression of being closed. Subsequently two further discharges of 

 spores were observed. There was an interval of a few minutes 

 between two successive discharges. Again, each sterigma, im- 

 mediately after discharging its spore, appeared to be pointed at 

 its end and devoid of any terminal drop of fluid. Even when 

 three spores had been discharged, I was unable to observe any 

 collapse of the basidium. All four sterigmata appeared to be 

 equally turgid. The fourth spore remained on its sterigma for 

 more than half-an-hour after the discharge of the third and was 

 not seen to disappear. In several other instances one or two 



1 Massee, in his Text-Book of Fungi (London, 1906), says : " In the Hymeno- 

 mycetes the mature spore is cut off from the apex of its sterigma by a transverse 

 wall. The sterigma retains its parietal protoplasm after the spore is cut off, and 

 its elastic wall continues to stretch as the tension due to the accumulation of 

 water increases. When the tension reaches a certain point, the wall of the 

 sterigma ruptures in a circular manner just below the septum at its apex ; the 

 elastic wall of the sterigma instantly contracts and forces its contained water to 

 strike the apical transverse wall, which is thus thrown off along with the spore 

 seated upon it." The reader is unfortunately left in doubt as to the authority 

 upon whom reliance has been placed for these statements. The account of spore- 

 discharge, however, is similar to that of Brefeld and merits the same criticisms. 



2 Chap. XL 



