4o6 RESEARCHES ON FUNGI 



sterilised bread (1 part bread, 4 parts water) where, within about 

 three weeks, it gave rise first to a little forest of stilbum-hodies and 

 afterwards to a number of the much larger perfect Omphalia agarics 

 (cf. Fig. 204). Both stilbum-hodiefi and perfect agarics were also 

 obtained by sowing stilbum-heads (1) on bread sterilised in conical 

 flasks and (2) on living leaves of Bryophyllum calycinum (for 

 details vide infra). ^ Thus Ashby's conclusions as to the behaviour 

 of Omphalia flavida in artificial cultures have been confirmed. 



The Structure of the so-called Stilbum-body. — The structure of 

 the stilbum-hody was first investigated and illustrated by Putte- 

 mans.2 With the hope of throwing light on the mode of abscission 

 of the head from the stalk, it has been carefully re-investigated by 

 Miss Ruth Macrae and the author in the laboratory at Winnipeg. 

 The description which here follows is based on observations made 

 by us on living material grown on malt-agar and also on Bryophyllum 

 and Oleander leaves. 



A stilbum-hody is, as we have seen, a minute pin-shaped structure 

 consisting of a slender cylindrical stalk surmounted by a head which, 

 when fully developed, can be readily detached (Fig. 205, A, B, C). 

 Both stalk and head are yellow. The stalk, which tapers gradually 

 from below upwards, is about 2-0 mm. in length, about 0-12 mm. 

 in diameter at its base, and about 0-05 mm. in diameter just below 

 the head, while the head has an average diameter of about • 36 mm, 

 varying up to • 4 mm. A stilbum,-hody never produces any spores.^ 



1 A. H. R. BuUer and T. C. Vanterpool, " The Bioluminescence of Omphalia 

 flavida, a Leaf-spot Fungus," Phytopathology, Vol. XVI, 1926, p. 63. 



2 M. A. Puttemans, "Sur la maladie du Cafeier produite par le Stilbella flavida,'^ 

 Bull. Soc. Myc. France, T. XX, 1904, pp. 158-164, PI. XI. 



3 M. C. Cooke {Grevillea, Vol. IX, 1880-1881, p. 11) and Kohl {vide infra) thought 

 that conidia are produced on the exterior of the head ; but the careful researches of 

 Puttemans (foe. cit., pp. 160-163), which are supported by the observations of 

 Patouillard, Massee, Spegazzini, Delacroix, Ashby, and myself, lead to the conviction 

 that Cooke and Kohl were mistaken. Cooke was probably misled by the Stilbum- 

 like appearance of the fungus and, as Puttemans argues, by an optical illusion in 

 respect to the appearance of the outer hyphae of the head. Kohl, whose description 

 of the stilbum-hea,d and its outer hyphae is imperfect and unsatisfactory, states that 

 for months he sought in vain for conidia before finding any and that many attempts 

 to infect Coffee leaves with the supposed conidia completely failed. He concluded 

 that, under natural conditions, the fungus is propagated not by the conidia but by 

 the detached heads. 



