458 RESEARCHES ON FUNGI 



one another by well-marked spaces ; whereas, in the Gastromycetes, each 

 basidium often bears more than four spores, and the spores are often 

 crowded together on the end of the basidium-body so that at maturity 

 they touch one another. This difference, again, is correlated with the 

 fact that in the Hymenomycetes the spores are violently discharged, 

 whereas in the Gastromycetes they are not. 



A toy balloon resembles a spore in having an enormous surface area 

 relatively to its mass. The author has invented a balloon gun with to3 T 

 balloons for projectiles. The trajectory of a balloon shot horizontally 

 resembles the trajectory (sporabola) of a spore shot horizontally from its 

 sterigma. 



The rates of fall of thistle-down, basidiospores, and bacteria have been 

 compared. The spores of Hymenomycetes fall much more slowly than 

 thistle-down, but much faster than bacteria. To fall a single inch in 

 still air certain very small bacteria require somewhat more than three 

 hours. To calculate the rate of fall of bacteria the author has employed 

 the equation for Stokes' Law as corrected by Millikan. 



Chapter II.- The interval of time which elapses between the first 

 appearance of a spore on the end of its sterigma as a tiny rudiment 

 and the moment of spore-discharge has been measured for a number 

 of Agaricineae. In Collybia velutipes it was found to be only about 

 47 minutes and in Panaeolus campanulatus about 7 hours and 30 minutes. 

 The interval is usually very short (50-90 minutes) for spores having thin, 

 smooth, colourless walls and much longer (3-9 hours) for spores having 

 thick, pigmented walls or walls which are polyhedral or warted. In 

 general, the interval is short for the spores of the Leucosporae and long 

 for the Chromosporae (chromosporous Agaricineae). The longest interval 

 observed was about 32 hours for Coprinus sterquilinus. In this fungus, 

 on any small area of the hymenium, the basidia all develop their spores 

 simultaneously. 



The ripening of a spore, after the spore has attained full size, takes 

 a longer time than the growth of the spore to full size. Thus in Collybia 

 velutipes the spores take about 15 minutes to grow to full size and a 

 further 32 minutes to ripen and become discharged ; and in Psalliota 

 campestris the spores take 40 minutes to grow to full size and a further 

 period of about 7 hours and 20 minutes to ripen and become discharged. 



Chapter III. When the parasite Hypomyces lactifluorum attacks 

 Lactarius piperatus, the host fruit-bodies grow to normal size but fail 

 to develop gills and remain completely sterile. On the other hand, the 

 Hypomyces gives rise to great numbers of perithecia on the under side 

 of the pileus. The author discusses the relations between the parasite 

 and its host, and describes his observations upon the discharge of spores 

 from the perithecia. 



Occasionally the fruit-bodies of certain Hymenomycetes grow to 

 full size but remain partially or completely sterile. Some fruit-bodies of 



