20 INTRODUCTION TO THE STUDY OF FUNGI 



from the mycelium formed during the fall of the previous year, 

 and this mycelium has rested in the ground for twelve months. 

 In digging up old pasture ground, or the dead leaves of an 

 autumn which has passed, mycelium in a resting state is 

 invariably found. We can hardly conceive of the preservation 

 of the spores of an Agaric through the winter and an entire 

 year, until the succeeding autumn, in any other way than by 

 the production of a hibernating mycelium. The spores them- 

 selves have too delicate an epispore to resist the effects of cold, 

 and we know from analogy that the resting spores of Algae 

 and Fungi, when known to be such, are provided with a special 

 thick outer envelope. The spores of Agarics are not thick 

 coated, and are incapable of hibernation ; hence we-a*e-driven 

 to the alternative of a perennial mycelium. A theory was 

 once propounded that a conjugation takes place in the threads 

 of mycelium which results in the production of a fertile Agaric, 

 the whole of whose fructification is thereafter rendered fertile, 

 but this view has never been accepted. Notwithstanding all 

 the theories, we are still in search of the process of fecundation 

 in Hymenomycetal Fungi. All that we can contend for is the 

 persistency of the mycelium as the means whereby the Mush- 

 room Fungi are carried through the winter and reproduced in 

 the succeeding year. 



There is a prevalent opinion, in Germany at least, that 

 " root fungi " are not always injurious to trees, but sometimes, 

 on the contrary, beneficial. Frank 1 states that certain trees 

 are unable to derive nutriment direct from the soil, but do this 

 by means of a mass of Fungus hyphae which entirely invests 

 the root, to which he gives the name of Mycorhiza. It makes 

 its appearance first on young seedlings, and is replaced by 

 fresh formations on older roots. He found it on the roots 

 of every tree examined belonging to the Cupuliferae, and 

 occasionally on willows and conifers, but considers it may 

 only be formed in soils which contain a large amount of 

 humus, or undecomposed vegetable remains. Through the 

 Mycorhiza the tree absorbs not only water and mineral con- 

 stituents, but organic substances derived from the humus. 

 Two or three other authors have since confirmed this in 

 1 Journ. Roy. Micr. Soc, vol. v. (1885), p. 844 ; vol. vi. (1886), pp. 113, 663. 



