INJURIES INDUCED BY PLANTS 223 



Even under the most favourable circumstances, M. lacrymans 

 can only appear after infection by spores or pieces of mycelia, 

 and on this account it is important to determine how the spores 

 or mycelia are distributed and carried about. 



I have already mentioned above that, under certain circum- 

 stances, the spores may be brought with the timber from the 

 forest. Such cases, however, must be extremely rare, at least 

 under the conditions of forest conservancy that obtain in 

 Germany, where large quantities of timber are seldom 

 stored in the forest to admit of the development of M. 

 lacrymans, which has hitherto been observed but once in such 

 a situation. That timber may be infected and attacked by 

 M. lacrymans during long storage in the forest naturally follows 

 from what has been said. But as a rule infection occurs only in 

 the towns, either in the wood-yards of carpenters, cabinet-makers, 

 &c., or in houses. It happens often enough in wood-yards that 

 the timber of old houses, which is still useful for certain 

 purposes, is stored beside sound wood, so that the rain washes 

 any loose spores and bits of mycelium on to the sound wood. 

 Workmen, especially carpenters who, let us say, have been 

 executing repairs in a structure affected by M. lacrymans 

 easily introduce the spores into new buildings, by proceeding 

 from the one to the other without changing or cleaning their 

 clothes, boots, or tools. 



For M. lacrymans to appear it is not merely necessary that 

 spores or mycelia should be present, but the conditions necessary 

 for their development must also be favourable. The spores 

 germinate only in the presence of alkalis. This explains the 

 disastrous consequences of employing humus-substances or 

 wood or coal ashes as packing materials, or allowing the work- 

 men to pollute the building with urine. The further growth 

 and vigorous development of the fungus are, however, most 

 encouraged by the use of damp materials, e.g. damp wood, 

 damp packing, damp stones, &c., because moisture is neces- 

 sary for the growth of M. lacrymans as well as every other 

 plant. 



This is no more the place to go into further details regarding 

 preventive measures to be taken in building a house than it is 

 to describe the measures to be instituted when M. lacrymans 



