PILOBOLUS UMBONATUS 



171 



first day the length was about 7 mm., on the second day about 

 5 mm., on each of the next five days 2-3 mm., and on the next day 

 only about 1-5 mm. The reduction in length of the fruit-bodies 

 was chiefly due to a shortening of the stipe and, no doubt, was 

 associated with a gradual diminution of the food supply. The 

 sporangia were shot away in the usual manner, and sporangium- 

 deposits were obtained upon glass slides. 



As compared with Pilobolus longipes and P. Kleinii, P. umbonatus 



Fig. 83. — Photomicrograph of spores of three species of Pilobolus ; 

 P. umbonatus (very small, pale, ellipsoid) ; P. Kleinii (much 

 larger, darker, ellipsoid) ; and P. longipes (three only to the 

 right, rounded-oval, very large and dark). Magnification, 510. 



is to be regarded as a smaller and more dehcate species. This may per- 

 haps be reahzed by comparing Figs. 81, 84, and 88, which respectively 

 show a rather small, a very large, and a medium-size fruit- body of 

 P. umbonatus, with Fig. 85, which shows a medium-size fruit-body of 

 P. longipes, and with Fig. 86, which shows two medium-size fruit- 

 bodies of P. Kleinii. All these Figures have the same magnification. 



The spores are ellipsoid and very small, their dimensions being 

 5- 0-6-0 X 3 -0-3 -8 \i. Singly they appear quite colourless, but in 

 the mass they are yellow. 



The photomicrograph reproduced in Fig. 82 shows a mass of 

 Pilobolus umbonatus spores together with five of the rounded-oval. 



