THE PILOBOLUS GUN AND ITS PROJECTILE 53 



comes to contain a considerable mass of red protoplasm. This 

 protoplasm contains vacuoles, and a streaming movement can be 

 readily observed in it. As a tuber is forming, the main hypha 

 adjacent to the tuber may become somewhat moniliform in outline 

 (Fig. 21, C-G, m). On attaining maturity, each tuber becomes 

 separated from the rest of the main hypha on which it is situated by 

 two septa, one at each of its ends (Fig. 21, E-G). The lateral hyphae 

 attached to a tuber were produced by the mycelium before the tuber 

 came into existence and are therefore not comparable to rhizoids. 

 Each of them eventually becomes separated from the tuber by a 

 septum. As shown by Lepeschkin's experiments with isolated 

 tubers, a mature tuber contains all the materials, except sufficient 

 water, necessary for the formation of a fruit-body.^ On this account 

 Morini has called it a trophocyst.^ 



Soon after a tuber has been formed and cut off from the hypha 

 with which it is connected, it begins to germinate : at one end it 

 develops a coarse hypha which grows up into the air (Fig. 21, E-G) 

 and eventually becomes differentiated into the stipe, the sub- 

 sporangial swelling, and the sporangium. The tuber itself becomes 



Fig. 21.- — Pilobolus longipes. Origin and early development of the fruit-body 

 primordium (tuber or trophocyst). Culture medium, cleared dung-agar. A, 

 part of a thick main hypha of a well-developed mycelium ; it is reddened with 

 carotin. B, another main hypha which is forming a fruit- body primordium 

 by swelling laterally for some distance along its length ; red protoplasm is 

 collecting in the swelling. C, a primordium, }3, which has attained full size, 

 it is filled with red protoplasm ; one of the main hyphae, in, which has passed 

 its contents into the primordium, has become moniliform. D, a primordium 

 which has developed to full size in the middle of a main hypha ; the inain hypha 

 has become moniliform at m ; the secondary branched hyphae have ceased to 

 grow in length. E, a primordium, cut off from the rest of a main hypha by 

 the cross-walls w w ; it has begun to form a fruit-body and is now differentiated 

 into a basal swelling b tuid a young stipe s. F, similar to E, but more advanced ; 

 at m the main hypha, which has now lost most of its contents, has become 

 moniliform. G, similar to E and F, but more advanced : w w, two cross-walls 

 which separated the fruit-body primordium from the rest of the main hypha ; 

 m, a part of the main hypha which has become moniliform ; b, the basal swelling 

 of the fruit-body ; s, the young stipe with red protoplasm densely aggregated 

 at its apex which is still imnaersed in the culture medium ; the basal swelling 

 and stipe contain a large central vacuole. The basal swelling of G is about 

 0-25 mm. long. Under natural conditions on horse dung, basal swellings often 

 attain a length of 1-2 mm. Magnification, 240. 



^ Cf. supra, p. 26. 



2 r. Morini, " Ricerche sopra una nuova Pilobolea," Mem. R. Accad. Sci. 1st. 

 Bologna, ser. 5, Vol. VIII, 1900, p. 86. Vide also his " Materiali per una monografia 

 delle Pilobolee," ibid., ser. 6, Vol. Ill, 1906, p. 118. 



