INJURIES INDUCED BY PLANTS 151 



the soil of certain beds by burning dry wood in parallel trenches 

 a foot deep and about a foot apart. The fire was kept up for 

 two days, so that the soil was practically roasted to the depth of 

 more than a foot. Seed was afterwards sown on these beds as 

 on the others. On the beds so treated the plants remained 

 sound for two years, but in the third year the old symptoms 

 reappeared. It is most likely that the fungus again invaded the 

 ground by means of gonidia carried from adjoining beds. It 

 would appear desirable, should circumstances make it advisable, 

 that the above plan should be experimentally tested. One 

 would thus discover whether infested seed-beds may continue 

 to be utilized without incurring much expenditure, or whether 

 it is better to change the ground. 



VALSA (MONOSTICHA) oxvsTOMA 1 



In Alpine districts a disease is very prevalent on Alnus 

 viridis, which, superficially examined, reminds one strongly of 

 the ravages of the larvae of Cryptorhynchus lapathi. Numerous 

 stems and branches contract the disease and die. It is chiefly 

 in August that the leafy branches become infected. The 

 withering of the cortex attracts attention to the presence of the 

 fungus, and directly afterwards small black tubercles appear 

 on the dead tissues. The stage of the development of these 

 pustules depends upon the length of time that has elapsed since 

 the branch died. Thus, although the presence of the fungus may 

 be detected on branches that are still living, it is met with in its 

 highest development only on such as are perfectly dead. The 

 progress of the disease down the tree is indicated by a sharp line 

 between the diseased wood, which is brown, and that which is 

 still sound. As the disease advances, other lateral branches 

 become affected. An exceedingly vigorous and very tough 

 mycelium is easily discoverable in the moribund wood, and 

 especially in the vessels. The lenticular tubercles consist of 

 black pseudo-parenchyma situated beneath the periderm. 

 Owing to their rupturing the periderm at the highest point 



1 v. Tubeuf, Forstlich-naturwis. Zeitschrift, October 1892. 



