NATURAL AND ARTIFICIAL INFECTION. 57 



advisable to lay portions of diseased leaves directly on healthy 

 ones, it is much better to place them near each other in a 

 moist chamber, hanging the former over the latter. 



When infection is carried on out-of-doors, it is best to obtain 

 a small plant which can be accommodated under a bell-jar. If 

 this be unattainable, it is often possible to bend one of the lower 

 branches down to the ground or other support, so that it can be 

 covered with a bell-jar. Again, a branch or portion of it may be 

 first sprinkled, then bound loosely up in a parchment-paper. 

 When carrying on infection it is of importance to avoid very 

 hot and dry or cold days ; moist, warm and cloudy days, or close 

 still nights, will be found best. In the case of diseases of the 

 rind, it is generally necessary to wound the periderm by a few 

 fine knife-cuts, then to place thereon a few drops of water with 

 infecting spores suspended in it. 



Artificial infection by means of mycelium is generally 

 attained by placing a diseased portion containing living my- 

 celium in contact with the healthy, so that the mycelium ran 

 grow from the one to the other. Thus, with bark-diseases, a 

 small portion of diseased rind is cut out and fitted into a 

 corresponding incision in the rind of the plant to be infected, 

 the oculation or graft being then protected against drying up by 

 gutta-percha, tree-wax, or parchment. The ingrafted portion 

 need not fit very accurately if well bound up, because the 

 mveeliuni will grow well in the moist chamber so formed. Tin- 



/ O 



most vigorous mycelium is generally found on the boundary be- 

 tween healthy and diseased parts, so that portions from this 

 region should be selected for infection. 



If the fungus under investigation frequents the wood, it is, as 

 a rule, a wound-parasite, so that for its infection the wood must 

 be laid ban-, and a diseased portion applied to it. If a branch is 

 to be infected ('.'/. with .\(riu, or < 'u<-n rliiturin), 'hen it should 

 be cut o\vr a bud, the exposed end split, and a line wedge of 

 diseased Wood inserted, the \\hole being bound Up. It is al-o 

 po-Hble to graft a diseased branch mi to a healthy. In the 

 Case "I' -teins, a portion of the healthy one should be relinked, a 



dl-ea-ed piece inserted, and the Wound closed oVer \\itll g HI ft 1 II _! - 



wax or clay. 1'ressler's growth-borer may in such cases be 

 ii-i'd with good ic-ults to obtain a c\ Under of di-ea-ed wood, 

 and to make a suitable receptacle for it in the -.omul plant. 



