582 RESEARCHES ON FUNGI 



shot away so that they escape freely into the air. The curvature 

 of the basidium is therefore fraught with a beautiful physiological 

 significance. 



The straight form of the basidium of most Hymenomycetes is corre- 

 lated with the crowding of the basidia into a compact hymenium, whereas 

 the curved form of the basidia of the Uredineae is correlated with the 

 absence of a compact hymenium. the isolation of the basidia, and the 

 origin of the basidia from teleutospores. 



The author describes the structure and development of the basidia 

 of Puccinia malvacearum and, with the help of an illustration, shows how 

 they are arranged in respect to the host-plant when they are discharging 

 their basidiospores. 



Chapter III. — The author treats of the cell-walls of basidiospores, 

 teleutospores, uredospores, and aecidiospores, and attempts to show that 

 their thickness, their smoothness or roughness, and the number and 

 arrangement of their pores are correlated with the function which each 

 kind of spore actually performs. 



In Phragmidium the -multicellular condition of the teleutospore and 

 the presence of two or more pores in each cell is correlated with the 

 looseness of the teleutospore-sorus, i.e. with the isolation of each teleuto- 

 spore from its fellows and the presence of interteleutosporic spaces in 

 which the basidia can develop. 



The number of aecidiospores present on three Barberry leaves heavily 

 infected with Puccinia graminis was calculated to be 3,700,000, 5.400.000, 

 and 8,000,000 respectively. 



The observations of Zalewski, Dodge, and the author prove that 

 the ripe aecidiospores of the aecidia of Puccinia, Uromyces. etc., are 

 shot violently into the air. The author has observed the discharge of 

 aecidiospores in Uromyces Poae, Puccinia graminis, P. pulverulenta, 

 and P. Poarum. 



The aecidiospores of Puccinia graminis, in damp still air, under 

 laboratory conditions, are shot up individually to a height of 3-4 mm. 

 above the mouths of the aecidia, and to a maximum height of about 

 7-8 mm. Sometimes clusters of aecidiospores composed of many cells 

 (60-150), which may be called aecidiospore-bombs, are shot from the 

 aecidium to a height of 7-8 mm. or to a horizontal distance of about 

 1 cm. 



In general, the observations of Zalewski. Dodge, and the author show 

 that the aecidiospores of typical aecidia (Puccinia, Uromj'ces, etc.) are 

 shot outwards from the mouths of the aecidia to a distance, varying 

 with the species, of 0" 4-2*0 cm. 



Aecidiospores are discharged most freely under very moist con- 

 ditions ; and, at the moment of discharge, every aecidiospore is in a 

 state of turgidity. The author suggests that discharge is caused by a 

 sudden overcoming of the resistance due to the adhesion of the adjacent 



