72 



.TOTRXAL OF AGRICULTURE OF P. R. 



say, .'J wound — and for this reason fungi of this kind are known as 

 wound parasites. In the presence of moisture the spores germinate 

 on the surface or preferably in the crevices of the wound, producing 

 <•( tlireadlike structure \v!'ieli penetrates^ the wood, dividing and sub- 

 dividing as it progresses, and ultimately forming a complete net 

 (invisible to the eve^i in the iny;idcd areas. Penetration of the hard 

 wood tissues is brought about by the action- of certain digestive 

 fluids secreted hy these fungus threads, or hyphae as they are called. 

 After the growth of the fungus, and the accompanying break- 

 ing doAvn of the wood, have progressed for a considerable length 



of time, often for many years, fruiting bod- 

 ies are formed. These are always produced 

 at some points where tlie decay has reached 

 tlie surface, and take different forms with 

 the various species involved. The more com- 

 mon of these are tlio familiar shelf or bracket 

 fungi {Polystictus spp.). (See Fig. (i.) 



On the lowTr surface of each bracket or 

 fruiting body will Ix' found a layer of very 

 small, cylindrical 

 i)ores, in w h i e h 

 :ire produced the 

 spores. Each of 

 these spores, and 

 great numl)(M's 

 are produced in 

 each pore, is ca- 

 |)abl(' of again starting wood rot wlicn it 

 reaches a suitable location. They are car- 

 ried ])y wind, water, birds, and other agen- 

 cies to fresh wounds. Another very com- 

 mon type {Svhizoplnjllum) produces nu- 

 merous gray, oyster-shell shaped fruiting 

 bodies, hairy on the u])per surface, and 



Ix'low in place of a layer of pores, producing a sei-ies of gills or la- 

 iiiella^ on which the spoi'es are borne. (See Fig. 7.) 



The tiia liner in wliich infection occurs has already been suggested, 

 but because of 1he importance of this point in connection with pre- 

 vention, some details will be given. Under normal conditions, the 

 outer bark presents an effective barrier to the entrance of rot, but 

 as soon as this protective area has been broken, a way is ojieiied for 



Fig. 6. — FoUisllvtus inn-si- 

 lus. The fruiting bofl- 

 ies of one of the cmii- 

 iTion wo()(l-rottin<>- t'nnyi. 



Fk;. 7. — Schizophyllnm com- 

 wuiic. Fruiting liodies of 

 tlio split gill niushrooni, Ji 

 very common wood-rotting 

 fnngns. 



