TRICHODERMA LIGNORUM 



173 



the formation of a closely-meshed network in the mycelium of 

 Peziza Sclerotiorum. In all these Ascomycetes, and in many others, 

 the union of a number of relatively weak and otherwise competing 

 mycelia, with the formation of a single strong compound mycehum 

 in which the units may co-operate in the 

 production of one or more fruit-bodies, must 

 often be of considerable advantage in the 

 struggle for existence. 



The occurrence of hyphal fusions and 

 of social organisation in the Pyrenomycetes 

 may be illustrated by some observations of 

 my own on the conidial stage of Hypocrea 

 rufa. This conidial stage, as was proved by 

 the anatomical studies of Tulasne ^ and by 

 the cultural experiments of Brefeld,^ is 

 nothing more or less than the well-known 

 fungus Trichoderma lignorum, which for 

 systematic purposes is usually placed in the 

 Fungi Imperfecta Trichoderma lignorum 

 forms rounded, somewhat lens-shaped, 

 green, conidial mats on dead bark, wood, 

 leaves, and other wet and decaying plant 

 remains in both Europe and North America, 

 more especially in late autumn and winter. 



Trichoderma lignorum invaded a large 

 sterilised horse-dung culture, which had been 

 prepared for the cultivation of Coprinus 

 sferquilinus, and grew there luxuriantly so 

 that, eventually, it spread over the entire 

 surface of the dung. I sowed several hundreds of the green 

 conidia in a hanging drop of horse-dung juice. The spores swelled 

 up and germinated, and the germ-tubes or young monoconidial 

 mycelia all became united into a single network which was 



1 L.-R. and C. Tulasne, loc. cit., Tomus III, Tab. Ill, Fig. 9. 



2 O. Brefeld, loc. cit.. Heft X, 1891, p. 190, Taf. V, Figs. 56 and 57. Brefeld 

 sowed the ascospore-halves of Hypocrea rufa and, after eight days, the mycelium 

 so produced developed the typical, branched, more or less pyramidal conidiophores 

 and the green conidia of Trichoderma lignorum. 



Fig. 98. — Trichoderma 

 lignorum,. Union of 

 mycelia derived from 

 different conidia. 

 Conidia placed in a 

 drop of dung-agar 

 two days previously ; 

 the germ-tubes have 

 fused with one 

 another and with the 

 conidia, so that a 

 compoimd netted 

 mycelium has been 

 formed. Drawn by 

 A. H. R. Buller and 

 Ruth Macrae. Mag- 

 nification, 467. 



