GENERAL PHYSIOLOGY OF FUNGI 67 



special adaptations: (i) the protrusion of theripeasci beyond the general 

 surface of the fruit body; (2) the diurnal periodicity in the ripening of 

 successive groups of asci; (3) the positive heliotropism of the asci; (4) 

 the considerable distance to which the spores are ejected (sometimes 

 30 cm.) with which is associated; (5) the large size of the asci and spores; 

 and (6) the chnging of the eight spores together, while describing their 

 trajectory through the air. The forcible explosion of the sporangio- 

 phore of Pilobolus crystalUnus by which the whole sporangium is dis- 

 charged a considerable distance into the air is due to the tension exerted 

 by gases and water vapor within the swoUen sporangiophore. 



The escape of biciliate zoospores (swarm spores) in such genera of 

 aquatic fungi as Achlya and Saprolegnia is through a terminal pore in 

 the zoosporangium. It appears that the discharge is associated with 

 the motility of the ciUa. In the moulds (Mucorace^), the sporangial 

 waU which is coated with minute particles of calcium oxalate becomes 

 soluble in water at matvurity and the intersporal substance swells up 

 assisting in the liberation of the spores. The entire inner peridium 

 about the size of a pin's head is forcibly ejected in the gasteromycetous 

 fungus, Sphcerobolus stellatus, and this is due to the unequal tension of 

 the different peridial layers. 



The disposal of spores and conidia is facilitated by water in the 

 case of the motile zoospores of such fungi as Achlya prolifera, Phytoph- 

 thora infestans and Saprolegnia ferax, where ciUa come into play. 

 Many spores are no doubt carried passively by water currents. Wind 

 is, however, one of the chief agents in the distribution of fungous spores, 

 such as those of the puffbaUs, the rusts and the moulds, although the 

 distance that such spores are carried is probably exaggerated. Flies, 

 which feed upon the strong-smelling slime in which the minute spores 

 of such fleshy fungi as Mutinus caninus, Icthyphallus impudicus are 

 imbedded, assist in the carriage of such spores and those of ergot 

 {Claviceps purpurea) in the Sphacelia stage, where viscid drops exude 

 that are attractive to flies, and although some flies arekilled by it, yet 

 svifficient escape to carry the spores. Slugs and snails by crawHng 

 alternately over diseased and healthy plants, probably disseminate 

 spores. That birds serve as distributors of spores is indicated by the 

 studies of Heald with the chestnut blight fungus, Endothia parasitica, 

 in which he found that a single downy woodpecker carried as many as 

 657,000 pycnospores. Certain subterranean fungi such as truflBes are 



