278 . ' Studies in Forestry [CHAP. xin. 



the roots, or at any wound-surfaces like those of broken 

 branches. 



These hyphae either insinuate themselves between the 

 cellular walls of the parenchym or the prosenchym, and vege- 

 tate in the intercellular spaces or the resin-ducts, whilst they 

 send single short off-shoots or suction-roots (haustoria) into 

 the interior of the cells, or else they bore through the cell- 

 walls, and thus force their way from one cell to another. By 

 extending in length, and at the same time throwing out side- 

 processes less frequently by ramifying they at length form 

 a filamentous network or Mycelium, which represents the 

 complete vegetative body of the organism. Masses of myce- 

 lium form Sclerotia, containing stores of food-supplies (chiefly 

 proteids and oil) which, under favourable conditions, produce 

 either new mycelium or sporophores of the fungus. 



Receptacles or spore-producers spring from the mycelium and 

 produce the reproductive organs, the spores. One and the 

 same fungus often produces sporophores of the most varying 

 shapes, and the form of these is much more characteristic (e. g. 

 mushrooms, toad-stools, &c.) than the hidden mycelium, which 

 is much alike in all fungi. 



When the sporophores are only single threads from the 

 mycelium they are called spore-hyphae, but in other cases the 

 sporophores or receptacles are of the most varying forms, and 

 have different names. Carpospores are spores which produce 

 a second generation differing from the original form, whilst 

 Gonidia or Conidia only reproduce the form on which they 

 occur. Gonidia therefore multiply one form of fungus very 

 rapidly within the annual period of vegetation, whereas carpo- 

 spores perpetuate the species from one year to the other. 



The spread of infectious diseases can take place either by 

 mycelial infection from root to root under the ground (as in 

 Trametes pini, Agaricus melleus, and Rosellinia quercina in 

 plantations, and Dematophora necatrix in vineyards), or by 

 spores and gonidia wafted about by the wind or conveyed 



