90 PHYSIOLOGY. 



not true roots, they function as roots, or root hairs, in the ab- 

 sorption of food materials. In old cellars and on damp soil in 

 moist places we sometimes see fine examples of this vegetative 

 part of the fungi, the mycelium. ]!ut most magnificent examples 

 are to be seen in abandoned mines where timber has been taken 

 down into the tunnels far below the surface of the ground to 

 support the rock roof al)0ve the nnning operations. I have 

 visited some of the coal mines at ^^'ilkesbarre, Pa., and here on 

 the wood props and doors, se\'eral hundred feet below the surface, 

 and in blackest darkness, in an atmosphere almost completely 

 saturated at all times, the mycelium of some of the wood-ciestroy- 

 ing fungi grows in a profusion and magnificence which is almost 

 beyond belief. Fig. So is from a flash-light photograph of a 

 beautiful example 400 feet below the surface of the ground. 

 This was growing o\"er the suriace of a wood pro[) or post, and 

 the picture is much reduced. ( )n the doors in the mine one can 

 see the strands of the mycelium which radiate in fan-like figures 

 at certain places near the margin of growth, and farther back the 

 delicate tassels of mycelium which hang down in fantastic figures, 

 all m spotless white and rivalling the most beautiful fabric in the 

 axquisiteness of its construction. 



190. How fungi derive carbohydrate food. — The fungi being devoid of 

 chloroph\'ll cannot assimilate the C( )._, from tlie air. They are therefore 

 dependent on the green plants for their carbohydrate food. Among the 

 saprophytes, the leaf and wood de; troying fungi excrete certain substances 

 (known as enzymes) which dissoh'c the carbohydrates and certain other 

 organic coni[)ounds in the wood\' or le;if\' substratum in which Ihey gro\\ . 

 They thus produce a sort of extracellular digestion of carlK.>h\'dratcs, con- 

 verting them into a soluble form \chi( h can be absorbed by the mvcelium. 

 The ]»arasi(ie fungi also obtain their carboh\-drates and other organic food 

 from the host. The m\Tcliunt of certain parasitic, and o{ wood destroying 

 fungi, excretes en/vmes (cytasc) which tlissolve minute peiforations in the 

 cell walls of the host and thus aid the hypha during its boring action in 

 penetrating cell walls. 



NOTK. — (.'eriain wood destro\-ing fungi growing in oaks absorb tannin 

 rlirct tl\', i.e. in an unchanged form. < )ne nl" Ihe pine destro\ing fungi 

 {TraDiclrs />iin} alisoi-bs the xNJogcn from lire wood (■Ms, lea\"ing the pure 

 I ellulo.se in whii II the A\lngen was filli;Urd; while Polyporns Dwllis absorbs 

 the cellulose, lea\'ing behind only the woiiel clement. 



