RESEARCHES ON FUNGI 



It is characteristic of both vegetative and sexual fusions that 

 hyphae or sexual organs destined to fuse act upon one another 

 at a distance. 



Action at a distance between fusion-elements appears to have 

 been first noticed by de Bary. 1 In 1881, he pointed out that, in 

 Pythium de Baryanum, the oogonium is formed first and that then 

 the oogonium stimulates neighbouring hyphae to send out antheri- 

 dial branches which grow toward it and eventually bring about the 

 fertilisation of the oosphere. 



Action at a distance in respect to sexual fusions was also observed 

 by Blakeslee 2 in the Mucorineae. In 1904, he remarked that in 

 paired cultures of Mucor Mucedo two conjugating zygophores, one 

 derived from a ( + ) mycelium and one derived from a ( — ) mycelium, 

 grow out into the air, stimulate one another, and grow toward one 

 another until they meet (c/. Vol. IV, Fig. 84, p. 153), and he referred 

 to the mutual attraction of the zygophores as being zygotactic. 



Action at a distance in respect to ordinary vegetative fusions 

 was recognised and clearly analysed by Marshall Ward 3 in 1888 in 

 his account of a Lily disease caused by Botrytis. He rightly main- 

 tained that in certain fusions (cf. Fig. 14, p. 29) the action at a 

 distance is of two kinds : ( 1 ) an action by one hypha causing another 

 hypha to send out a side branch toward it and (2) an action which 

 causes the first hypha and the branch to grow toward one another 

 until they meet. Said Ward 4 : 'It seems to me, after observing 

 numerous cases of these fusions in this and other fungi, that we must 

 distinguish between two steps in the process. In the first place 

 there is some cause at work which determines the formation of a 

 branch, and then, in the second place, we have to assume that some 

 other cause determines the direction in which the branch grows." 



In 1892, Rothert 5 described the formation of hyphal fusions in 



1 A. de Bary, " Untersuchungen iiber die Peronosporeen und Saprolegnieen und 

 die Grundlage eines natiirlichen Systems der Pilze," Beitrage zur Morphologie. und 

 Physiologie der Pilze, Frankfurt, Reihe IV, 1881, p. 85. 



2 A. F. Blakeslee, " Sexual Reproduction in the Mucorineae," Proc. Amer. Acad. 

 of Arts and Sciences, Vol. XL, 1904, p. 274, Plate II, Figs. 25-27. 



3 Marshall Ward, " A Lily-Disease," Annals of Botany, Vol. II, 1888, pp. 319-382. 



4 Ibid., p. 330. 



W. Rothert, " Ueber Sclerotium hydrophilum Sacc, einen sporenlosen Pilz," 

 But. Zeit., Jahrg. L, 1892, pp. 358-359. 



