TAXONOMY OF THE PTLOBOLIDAE 211 



Stipe increasing slightly in diameter from below upwards, until just 

 beneath the subsporangial swelhng it is about 0-1 mm. in diameter. 

 Subsporangial swelling ellipsoid, its maximum diameter being about 

 midway between the base of the sporangium and the top of the stipe, 

 0-65 mm. long and 0-4G mm. broad; a pale orange-red band of 

 protoplasm at the junction of the stipe and the subsporangial 

 swelling. Sporangium decidedly umbonate and more or less conical, 

 0-21-0 -23 mm. in diameter or about one-half the diameter of the 

 subsporangial swelling, shrinking on drying after discharge and 

 becoming acutely pointed ; columella very bluntly conical or 

 rounded (when removed from a discharged sporangium its edge is 

 turned inwards towards the axis), greyish, distinctly darker than the 

 subsporangial swelling. Spores ellipsoid, singly almost colourless, 

 but yellow in mass J 5- 0-6-0 x 3-0-3-8 jj^. 



On horse dung, Winnipeg, Canada, and, according to a communi- 

 cation from the late Dr. Roland Thaxter (who observed the species 

 forty years ago but did not describe it), more frequently on sheep 

 dung, at Boston, U.S.A. 



Easily distinguished from all other species of Pilobolus by its 

 decidedly umbonate sporangium and its minute ellipsoidal spores. 

 With a hand-lens one can readily make out the acutely-pointed 

 umbonate shape of the dried discharged sporangia when these are 

 seen in lateral view. 



Illustration : Fig. 105. Other illustrations in this volume : 

 Figs. 81, 82, 83, 84, 87, 88, 89, 90, and 91. 



B. Siiorangium yelloiv uihen projected ; provided with 



an apophysis.^ 



9. Pilobolus nanus van Tiegh. Trois. Mem. in Ann. Sci. Nat. 

 ser. 6, vol. iv, pp. 340-2, pi. 10, f. 10-22 (1876). Orove. Pilobolidae, 

 p. 336, pi. 6, f. 2. Sacc. Syll. vii. 186. Palla, I.e., p. 398. 



^ In most Piloboli, the subsporangial swelling is not constricted below the level 

 of its attachment to the columella and the wall of tlie sporangium. In P. nanus, 

 according to van Tieghem, the subsporangial swelling is constricted a sliort way 

 below that level so that it is divided into two unequal parts, a lower globular sub- 

 sporangial swelling proper and an ujjper shallower swelling — the so-called apophysis. 



