268 RESEARCHES ON FUNGI 



Slugs are probably 6f but minor importance in dispersing the spores of 

 Hymenomycetes. 



Slugs do not find the fruit-bodies of all Agaricinse equally palatable, 

 but prefer to starve rather than eat those of certain species. 



PART II 



Chapter I. — The spores of some Discomycetes (Peziza, Bulgaria, 

 Gyromitra, &c.) are scattered by the wind, whilst others (Ascobolus immersus, 

 Saccobolus, &c.) are dispersed by herbivorous animals. Each mode of 

 spore-dispersion is correlated with special adaptations in the asci. 



The spores of Peziza repanda are shot up into the air to a height of 

 2-3 cm. The eight spores from an ascus separate from one another almost 

 immediately after leaving the ascus mouth, and are then carried off by the 

 wind. The fact that the ascus jet breaks up on leaving the ascus was 

 observed by means of the beam-of -light method. 



Puffing is probably not due (as de Bary supposed) to the mere with- 

 drawal of water from asci. Solutions of grape sugar, glycerine, sodium 

 chloride, and potassium nitrate, which merely withdraw water from the 

 ripe asci of Peziza repanda, do not cause their explosion. On the other 

 hand, solutions of many poisonous substances, e.g. iodine, mercuric chloride, 

 silver nitrate, copper sulphate, sulphuric acid, acetic acid, and alcohol, give 

 rise to marked puffing. Two alkalies — sodium hydrate and sodium car- 

 bonate — kill the asci without causing them to discharge their contents. 

 It seems probable that puffing is caused by a stimulus given to the proto- 

 plasm in contact with the ascus lid. 



The physics of the ascus jet in Peziza repanda has been discussed. It 

 seems probable that the separation of the eight spores of an ascus during 

 their upward flight into the air is due to considerable differences in the 

 initial velocities given to the individual spores upon their discharge. 

 Surface tension probably plays but a minor part in breaking up the ascus 

 jet. When the ascus is regarded as an apparatus for squirting out a jet 

 in such a manner that the jet immediately breaks up into eight parts so 

 that each part contains a spore, its structure becomes more intelligible. 



The eight spores in an ascus of Peziza repanda are loosely attached 

 together, and the row of spores is anchored to the ascus lid by a special 

 protoplasmic bridle. De Bary's hypothesis of currents is unnecessary in 

 accounting for the means by which the spores are caused to take up their 

 characteristic positions in the ascus. 



The wind-borne spores of Ascomycetes and of Hymenomycetes are 

 of the same order of magnitude with respect to their short diameters, 

 and are therefore equally well adapted to be dispersed by ordinary air 

 movements. 



