20 RESEARCHES ON FUNGI 



they meet with a Pilobokis or a Mucor they at once parasitise it. 

 Thus the parasitism of Mortierella, so far as Pilobolus and Mucor 

 are concerned, is purely facultative.^ Syncephalis ^ is also a 

 facultative parasite, while the parasitism of Piptocephalis ^ and 

 Dimargaris * is obligatory. 



At Winnipeg, cultures of Pilobolus longipes and P. Kleinii in 

 some years are much parasitised by Syncephalis nodosa. This 

 species, originally described by van Tieghem ^ in 1875 and recorded 

 by Seymour ^ as a parasite on undetermined Mucorineae in North 

 America, is characterised by having two or three nodular thickenings 

 on the mature and collapsed sporangiophore. 



My own observations on Syncephalis nodosa as a parasite of 

 Pilobolus may be here briefly recorded. The spores of *S^. nodosa 

 germinate readily in hanging drops of dung-agar. The mycelium, 

 as found on young Pilobolus sporangiophores, consists of very fine 

 hyphae which by means of hyphal fusions form a reticulum with 

 enlargements where two or more hyphae are joined together (Fig. 

 11, C-E).' It creeps over the surface of a Pilobolus stipe and 

 there forms irregularly swollen appressoria {cf. Fig. 10, a). From 

 an appressorium one or sometimes two hyphae are sent into the 

 interior of the stipe. These hyphae, which may have haustorial 

 swelhngs just inside the wall of the stipe, form a mycelium which 

 grows within the interior of the stipe, soon invades the subsporangial 

 swelling if this has been formed and, finally, stops the growth of 

 the host-plant (Fig. 11, A and B). The interior mycehum at various 

 points then makes its way out of the stipe. On the surface of the 

 stipe, here and there, a hypha swells up, branches and rebranches, 

 and forms what we may call a mat of basal hyphae (D and E). From 

 these thickened hyphae cylindrical sporangiophores grow outwards 

 into the air. When the sporangiophores have attained a height of 

 about 0-2 mm., each of them becomes clavately swollen at its apex 

 and then sends out terminally three or four processes which become 



1 P. van Tieghem, loc. cit., p. 97. ^ Ihid., p. 116. 



3 Ibid., p. 138. " Ibid., p. 157. ^ Ibid., pp. 131-133. 



^ A. B. Seymour, Host Index of the Fungi of North America, Cambridge, Mass., 

 U.S.A., 1929, p. 5. 



' Cotton-blue dissolved in lactic acid was used as a stain to show up the 

 Syncephalis mycelium against the stipe of the Pilobolus. 



