THE SPHAEROBOLUS GUN 297 



days. 1 (3) When large water drops (0-17 cc), falling from a tap 

 at the rate of about one per second for a distance of one foot, are 

 allowed to impinge on glebal masses which have been shot on to, 

 and have stuck to, a pane of glass, the glebal masses are not dis- 

 lodged in the course of five hours. 



The projectile, owing to its fatty contents, forms, as we have 

 seen, a glutinous mass which never becomes brittle, even when 

 dried. It is clear, therefore, that the strongest winds cannot break 

 it into pieces or disperse the spores and gemmae which it contains. 



Not only is the projectile not dislodged from its place of attach- 

 ment by water drops falling upon it (as recorded above) but, when 

 submerged in water in a beaker in the laboratory, it does not dis- 

 integrate in the course of many hours. The projectile, therefore, is 

 well-adapted to withstand the action of rain-storms under natural 

 conditions. 



Since the projectile has no means of its own for separating its 

 spores and gemmae from the fatty matrix in which they are em- 

 bedded, and since the projectile resists removal and disintegration 

 by wind and rain, it is clear that, if the numerous spores and gemmae 

 of a discharged projectile are ever to be disseminated under natural 

 conditions, the projectile must find its way passively into some place 

 where its fatty matrix can be dissolved. Such a position is actually 

 provided by the alimentary canal of a herbivorous animal. 



The sliminess of the exterior of a glebal mass just before and 

 just after its discharge is due to a slimy liquid which collects in the 

 open cup of the fruit -body and in which the glebal mass becomes 

 partially submerged (Fig. 161, B, e, p. 316). This liquid, which 

 Miss Walker 2 found can be drawn up with a capillary tube, doubt- 

 less functions as a lubricating agent : it prevents the projectile, 

 before and at the time of discharge, from sticking to the palisade 

 layer of the peridium, and it eases the separation of the projectile 



1 On November 14, 1923, I observed a projectile on a leaf of a Wolfberry bush 

 (Symphoricarpos occidentalis) in a pasture of the Manitoba Agricultural College. 

 After some rainy days had supervened and about a week after making my first 

 observation, I returned to the pasture and found the projectile still in its old place 

 on the leaf. For further field observations on Sphaerobolus projectiles vide infra. 



2 L. B. Walker, loc. cit., footnote, p. 154. She adds that the liquid " contains a 

 great deal of maltose as indicated by Fluckiger's reaction and by osazone formation." 



