THEPILOBOLUS GUN AND ITS PROJECTILE 51 



Fig. 19. — Pilobolus longipes. Photomicrograph of .spores 

 sown in dung-agar. Left, three spores which have not 

 germinated. Right, a spore which swelled up and 

 germinated. There are red particles in it and in the 

 mycelium. Magnification, about 400. 



Fig. 20. — Pilobolus longipes. Germination of sj)ores in cleared dung-agar and the 

 production of mj'celia. A, spores, just placed in the culture medium ; they are 

 reddish-yellow, owing to the presence of carotin dissolved in oil-drops. B, one 

 of the spores which has been crushed, to .show the thick cell-wall. C, 14 hours 

 after sowing, two spores which have swollen. D, 24 hours after sowing, three 

 spores which have emitted germ-tubes. E, 25 hours after sowing, a young 

 mycelium produced from a single germ-tube. F, 25 hours after sowing, a young 

 mycelium produced from two germ-tubes. G, 26 hours after sowing, a more 

 advanced mycelium developed from a single germ-tube. H, 03 hours after 

 sowing the spores, part of a mycelium showing a thick main hypha and slender 

 secondary hyphae. The main hypha has swollen locally and has formed a 

 fruit-bodj' primordium (tuber or trophocyst) filled with dense red protoplasm. 

 Magnification : A-F, 293 ; G and H, 60. 



