428 I'ROTHCTK^N AfJAINST PLANTS. 



are induced by certain conditions of soil and weather, the 

 whole of a wood almost simultaneously shows symptoms of 

 disease. An attack by fungi, on the contrary, is propagated by 

 infection from one or a few individuals which are first attacked, 

 and therefore starts from a centre, spreading generally in a 

 centrifugal manner, like the fairy-rings in a meadow due to 

 Mai'cismiiis oreadcs. 



5. Protective Measures ariaiust Funi/i. 



In order to prevent the attacks of fungi, good sylvicultural 

 rules must be observed as regards the regeneration and 

 tending of the crops of trees. 



The most important of these are : to grow species suitable 

 to the locality ; to cultivate the plants scientifically, and to 

 plant strong plants and in suitable mixtures, especially of 

 broadleaved trees with conifers ; early cleanings ; timely 

 thinnings ; pruning from November till January ; avoidance 

 of injuries to standing trees during fellings; tarring wounds. 



To combat the individual fungi successfully, their life- 

 history must be known. Special rules are : 



Isolation of attacked plants by trenches ; removal of 

 diseased plants ; pruning attacked branches ; destruction of 

 weeds that serve as hosts for injurious fungi ; spraying 

 diseased plants with fungicides * ; removal of infected 

 fallen needles or leaves. All infected material should be at 

 once burned i)i situ. 



Section II. — Fungi attacking Conifers. 



The next two sections give a list of the fungi which experi- 

 ence has showai to be injurious to forest trees, with a short 

 descrii)tion of their external appearance, the classes of woods 

 and localities liable to be infected, and the distribution -areas 

 of the fungi ; also an account of the damage done and the 

 means for combating it. The most injurious species are 

 marked with an asterisk. For a full description of the 

 pathology of each disease induced by fungi, reference is 



* r/". Lodeniaii, " The Spraying of Plants." Now York : TheMacmillan Co. ; 

 Loii.l.m, M;icMnill;ui .V: Co.. \wh. 



