HELIOTROPISM OF ASCI IN DISCOMYCETES 287 



also the Bladder Elf-cup} It commonly occurs on heaps of horse 

 dung and on manured soil in Europe and North America. 



The fruit-bodies of Aleuria vesiculosa are often clustered so that 

 they more or less distort one another by mutual pressure (Fig. 137) 

 but, not infrequently, they occur as isolated individuals. A single 

 fruit-body varies in diameter from 3 to 8 cm. At first, it is globose 

 and almost closed ; but, later, it expands to form a more or less 

 hemispherical cup which is brittle, somewhat translucent and, at 

 the base, about 3 mm. thick. The margin of the cup usually 

 becomes notched and may either turn outwards to a greater or less 

 degree or remain incurved. Below, where it enters the substratum, 

 the flesh of the cup is contracted centrallj^ to form a short stem-hke 

 base or stipe which breaks up in the substratum into strands of 

 myceUum (Fig. 138). The inner hymenial surface of the cup is 

 pale brown or fawn-coloured, while the outer lower surface is 

 brownish and coarsely granular or furfuraceous from the presence 

 of minute irregular warts. The flesh or trama is parenchymatous, 

 the central cells being large and watery. Sometimes the trama 

 sphts so that a cavernous air-space is formed between the hymenium 

 and the base of the cup. The hymenium is about 0* 36 mm. thick. 

 The paraphyses are unbranched and septate, the terminal cell being 

 slightly club-shaped and coloured yellow with oil-drops and the 

 shaft-cells at first cylindrical but becoming swollen at their sides 

 as the fruit-body becomes older. The asci are fairly large, about 

 360 [x long and 20 [x wide, sUghtly attenuated dowTiwards, turning 

 blue with iodine, those at the base of the cup straight and those at 

 the sides heUotropically curved toward the mouth of the cup. The 

 spores are elliptic, colourless, smooth, without internal oil-globules, 

 bearing on one side a little lenticular mass of colourless jelly which 

 swells up after discharge in water, about 20-24 [i long and 11-13 [j, 

 wide. 



The fruit-bodies of Aleuria vesiculosa used in my investigations 

 were obtained in part from manured ground at the Manitoba 

 Agricultural College and in part from laboratory cultures. To 

 procure hving fruit-bodies during the winter months at Winnipeg 



^ E. W. Swanton, Fungi and How to Know Them, London, 1909, p. 182. 



