SPORE DISCHARGE AMONG BASIDIOMYCETES 201 



miliaria mellea, Amanitopsis v agin at a, Rnssnla emetic a, Panus stip- 

 ticns, and Pleurotiis ostreatus. All exhibit the following features 

 during basidiospore discharge: (1) the four spores are discharged 

 in succession, not simultaneously; (2) a droplet of exudate appears 

 at the hilum of the basidiospore just before discharge and is absent 

 on the sterigma after discharge. It is carried along with the spore 

 and disappears as the spore strikes, causing it to adhere; (3) the 

 sterigmata and basidium do not collapse as the spores disappear. 



Violent basidiospore discharge is an important phenomenon in 

 this group because the spores, when liberated into the space be- 

 tween gills or spines or into pores, are prevented bv the position of 

 the pileus from touching each other or the hymenial surface. 

 Thev thus escape from the pilei. Each is shot horizontally for a 

 short distance, the motion being rapidly terminated because of 

 resistance of the air. In Amanitopsis vaginata horizontal move- 

 ment of the spore is completed in 1/400 second [Builer (1909)], 

 and the initial velocity approximates 40 cm per second. When 

 horizontal movement is at an end, the spores react in response to 

 gravity. Builer observed the rate of fall of basidiospores by use 

 of a horizontally placed microscope. He mounted sections of 

 hymenium in a chamber and placed the chamber on the micro- 

 scope stage. The hymenium was thus vertically disposed. Three 

 silk threads were then attached to the eyepiece at equal distances 

 from each other across the field of view. Records of the velocity 

 of spores passing through the field of view could then be made on 

 an electrically rotated drum connected with a tapping key that 

 could be depressed by the observer. By this means Builer (1909) 

 found that the velocity of fall in millimeters per second for 

 Colly bia dryophila was 0.37, for Plntens cervinus, 0.67, for Psal- 

 liota campestriSy 1.61, for Poly poms squamosns, 1.03, for Boletus 

 felleus, 1.22, for Rnssnla emetica, 1.64, for Amanitopsis vaginata, 

 2.95, and for Coprinns commatus, 3.96. Small spores fell at a 

 slower rate than larger spores. These rates of fall were found 

 to be considerably greater than expected from calculation by 

 Stokes' law, a discrepancy for which Builer was unable to offer a 

 satisfactory explanation. Presumably it is in part related to dimi- 

 nution in volume of the mass (spore plus droplet) as fall proceeds. 



Among other interesting facts established by these studies on 

 violent spore discharge among Hymenomycetes is that, so long 

 as corky and woody pilei have sufficient moisture, they may con- 



