THE SPHAEROBOLUS GUN 



313 



gun is undoubtedly located in the inner everting membranes, i.e. 

 in the fibrous layer and the palisade layer which are firmly attached 

 to one another. Of this I have obtained convincing evidence by 

 means of a simple experiment 

 which was carried out as follows. 

 After a fruit -body had opened 

 stellately and shortly before it 

 normally would have discharged 

 its projectile, the inner mem- 

 branes of the fruit-body together 

 with the glebal mass at their 

 base were dissected away from 

 the outer membranes, as shown 

 in Fig. 161, C, and set on a 

 moist surface in a damp-cham- 

 ber. After some time, the 

 little cup, consisting of inner 

 membranes only, suddenly be- 

 came everted in the usual manner 

 (Fig. 161, D) and discharged the 

 projectile to a distance. This 

 experiment was repeated several 

 times. It was also found that 

 the isolated inner membranes 

 discharged the projectile when 

 these membranes and the pro- 

 jectile, after being dissected 

 out of an opened fruit-body, 

 were completely submerged in 

 water. 



Miss Walker x investigated 

 the cause of glebal discharge and 



she, too, concluded that the inner membranes of the fruit-body 

 are alone responsible for the ejection of the glebal mass. In the 

 course of her work she removed the glebal mass from opened 

 fruit -bodies and replaced it with paraffin balls mixed with 



1 L. B. Walker, loc. cit., pp. 156-157. 



Fig. 158. — Sphaerobolus stellatus. Basi- 

 diospores produced in the glebal 

 chambers. A, six spores borne on 

 a single basidium which has a clamp- 

 connexion at its base. The spores 

 are crowded and attached to minute 

 projections on the basidium-body, 

 typical sterigmata not having been 

 developed. B, a six-spored basidium, 

 seen from above. C, twelve isolated 

 mature spores, to show their vari- 

 ations in shape and size. D, some 

 crushed spores, to show the thick- 

 ness of the walls. Drawn by 

 A. H. R. Buller and Ruth Macrae. 

 Magnification, 1060. 



