SAP-STAIN, MOLD, AND DECAY IF GEEEN WOOD. 17 



When supplied with the essentials necessary for growth, fungi 

 develop rapidly and often reproduce abundantly. Deprived of any 

 or all of these factors, however, the vegetative portion, i. e.. mycelium, 

 ceases to grow and eventually dies. In some cases, as, for instance, 

 certain molds, the spores may retain their vitality for long periods 

 under extremely unfavorable circumstances. When favorable con- 

 ditions return, these spores soon germinate and often develop an 

 abundant growth of mycelium within a few days. Fruiting bodies, 

 sometimes bearing countless spores, may then make their appearance, 

 and the life cycle is repeated. The ideal conditions for growth are 

 often to be found in green timber containing a high percentage of 

 sapwood when exposed to the stagnant atmosphere of the woods, 

 poorly ventilated sheds, warehouses, and cars during warm, sultry, 

 or rainy weather. Under such circumstances the sapwood may be- 

 come thoroughly infected within a few days. Sap-stain may thus 

 appear soon after infection with spores or mycelium of the sap-stain 

 fungi. Wood-rotting fungi may also get a good hold upon timber 

 under such conditions, and symptoms of incipient decay later be- 

 come apparent (PL I, fig. 6). 



DURABILITY OF STAINED OR MOLDED WOOD. 



Since the blue stain and mold fungi cause little or no dissolution of 

 the wood fibers, they do not affect directly the durability of the 

 timber. If properly piled and dried, stained or moldy wood stock 

 free from decay should not deteriorate further from the action of 

 the fungi. However, the conditions which favor the development 

 of sap-stain, mold, and sap-rot are much the same, namely, the 

 presence of spores or mycelium of the particular fungi capable of 

 producing these defects in wood, a substratum containing the 

 requisite food material, moisture, and a high relative humidity (75 

 to 100 per cent) , a temperature of 70° to 100° F., and a lack of circu- 

 lation of the air, or stagnation, which retards or prevents the proper 

 drying of the timber. There seems to exist among many lumbermen 

 a false notion that mold and sap-stain represent early stages in the 

 development of sap-rot, or " dote," as it is commonly called. While 

 the presence of an abundant growth of mold or sap-stain in green 

 stock indicates conditions which are likely to favor the growth of 

 rot, it is well known that the rot is caused by a distinct group of 

 true wood-destroying fungi which develop independently. 



Molds in general develop rapidly. Hence, they may be often 

 found growing profusely on green timber already infected with rot- 

 producing fungi long before the latter have exhibited any notice- 

 able evidence of their presence. It is possible, however, for wood 

 destroyers to infect and bring about the disintegration of wood which 

 contains no trace of mold or any other organisms. , 

 75579°— 22 3 



