THE SPHAEROBOLUS GUN 315 



cups in the usual manner. 1 She gives the following account of her 

 observations : 



" When a fruit -body first breaks open, the glebal mass is firmly 

 attached to the peridium at the base but can be removed with a 

 needle. After the basidiocarp has been open an hour or more, 

 the glebal mass lies as a ball entirely free from the peridial walls 

 and may be rolled over or removed with great ease. These glebal 



Fig. 160. — Sjihaerobolus stellatus. A pure culture on Willow wood, a, very 

 young sporocarps ; 6, full-grown sporocarps covered with the mycelial layer 

 of the peridium ; c, a sporocarp opening ; d and e, two sporocarps which 

 have opened stellately and now show the glebal projectile in the centre of 

 each cup ; /, g, and h, three sporocarps which have discharged their pro- 

 jectiles, the pearly dome over each of their mouths being the everted, 

 elastic, combined palisade and fibrous layers of the peridium. Enlarged 

 to three times the natural size from a photograph made by Leva B. 

 Walker. 



masses, which are slightly heavier than water, were removed at 

 various periods after opening and tiny balls of paraffin mixed with 

 sand to weight them to about the same specific gravity as the 

 original mass were substituted. These were as readily discharged as 

 the glebal masses. Pebbles of similar size were used as substitutes 

 and also drops of mercury the size of or larger than the glebal masses. 

 These were as readily discharged as the original projectile. During 

 the time intervening between the substitution of the artificial ball 

 for the glebal mass and the discharge, water accumulated in the 

 1 Using pebbles and small shot, I have successfully repeated these experiments. 



