GERMAN NOTES. 205 



On the strength of this Prof. Mayr laid it down as an axiom 

 that though the apothecia of the fungi produced on diseased 

 younger growth were highly infectious, those formed on the 

 dead and dying leaves of older forest trees were innocuous. 



He further supported his position by saying that no natural 

 reproduction of pines could take place if the disease could 

 be produced through the shed leaves of mature forests; and, 

 whilst he recommended the destruction of all young growth 

 killed or even attacked by the scab, he declared that the cover- 

 ing of young seedlings by pine branches was quite harmless. 

 Prof. Mayr, however, failed to make certain that the litter 

 collected in the forest actually contained leaves affected by 

 Lophodermium germs of any sort whatsoever. 



Haak made experiments on Prof. Mayr's lines, but took care 

 to make certain that the leaves collected in a 20-to-3o-year- 

 old thicket, a 40-year-old pole forest, and in a mature forest, 

 contained apothecia of Lophoderfnium . In examining the 

 leaves obtained from the various sources, he found that those 

 of the infected cultures bore the largest number of apothecia, 

 those of the thickets somewhat less, and those taken from the 

 old forests but few. 



All plants remained green on the areas where no litter had 

 been placed ; on those covered with leaves obtained from 

 diseased cultures the plants were all red ; on those treated with 

 leaves from thickets a very large percentage were red ; and on 

 those where the litter from the older forests was used nearly- 

 half the plants were scab-diseased. These results prove that 

 Prof. Mayr's experiments were not sufficiently exact, and that the 

 disease on old trees is identical with that which destroys the 

 young growth ; a fact which had already been proved in the 

 laboratory. 



The answer to the first question then is, evidently, that every 

 old pine forest bearing apothecia on its leaves may cause 

 the infection of young growth — and once this takes place the 

 disease will rapidly increase in virulence and form new hotbeds 

 of infection. 



The second question is. When and how does the infection take 

 place ? Opinions on this point again vary considerably, and 

 are not always on all fours with the facts of the case. 



Open apothecia have been found by careful searching at 

 nearly all periods of the year. Von Tubeuf found in the leaves 



