GERMAN NOTES. 209 



ceased or been reduced to a minimum, such leaves developing 

 apothecia after they have dropped. 



This is the reason why apothecia-infected leaves are found 

 in the litter of thickets and older forests, for if the leaves had 

 once dropped to the ground uninfected, the Lophodenniiim 

 germs would have had no chance against other more rapidly 

 growing saprophytes. The growth of the fungus is, as a rule, 

 confined to the leaves of young plants, and every new attack is 

 due to re-infection, but in some cases the mycelium enters the 

 very marrow of the plant itself. In these latter cases the young 

 pine is doomed, whereas, even in extreme cases when all the 

 leaves have been lost, the plant will, as a rule, throw out new 

 •ones in the second year; and a repetition of the infection can be 

 averted by syringing with a copper solution, in spite of the fact 

 that the apothecia of a single diseased plant may eject as many 

 as 60,000.000 spores. 



The danger of infection is considerably lessened with the 

 diminution of the number of plants on a given area, and hence is 

 less in the case of plantings than of sowings ; and in these again 

 it varies in accordance with the density of the young growth. It 

 takes usually several years before the young pines are killed out- 

 right, even in cases of annually repeated and unchecked infection, 

 and even then a certain, though small, percentage escape. 



The accompanying photos of four young seedlings (Plate II.), 

 grown on the same experimental scab bed, taken during the 

 fourth year of their existence, show the advantages to be derived 

 from the copper sulphate treatment. 



It has been suggested that the mycelium of the fungus, after it 

 had once entered the shoots of a sick plant, might, as in the case 

 of other well-known fungi, thence re-enter the new leaves and 

 maintain the disease from within, independent of a renewed 

 external infection. To prove or disprove the correctness of this 

 assertion Haak selected twenty-five plants, such as depicted in 

 Figs. 2, 3 and 4, and planted them, after the careful removal of 

 all red leaves, in an entirely scab-free area. They remained 

 green and are recovering, whereas all similar plants remaining 

 in the original place were, as early as December 19 10, entirely 

 red. It is thus proved that a new infection is essential to the 

 continuation of the disease, and this can be prevented by 

 proper treatment. 



More or less incomplete experiments led to the opinion that 



