Fortpflanzung. 251 



entstehen Tetraden mit überzähligen Zellen und Kernen. Die Embryosäcke von 

 Gros-Michel entwickeln sich sehr unregelmäßig. Bei der Appelbacove gibt es neben 

 degenerierenden Embryosäcken auch einzelne, die sich weiterentwickeln. Die 

 Degeneration tritt in verschiedenen Altersstadien ein; der Zeitpunkt derselben 

 läßt sich an der charakteristischen Form der Embryosäcke bestimmen. 



Aus den Unregelmäßigkeiten der Kernteilung läßt sich, wie eine Zusammen- 

 stellung von Tischler zeigt, kein Schluß darauf ziehen, ob die Eßbananen Ba- 

 starde seien oder nicht. Es gibt Fälle mit unregelmäßiger Kernteilung bei Nicht- 

 hybriden ebenso wie regelmäßige Teilungen bei Hybriden. Im Gegensatz zu 

 Tischler vermutet d'Angremond, daß die Eßbananen durch zufällige Kreuzung 

 entstanden seien und nachträglich durch die Kultur ihre weite Verbreitung ge- 

 wonnen haben. Nach Sagot besteht für Musa feJii die Möglichkeit, daß Stand- 

 ortseinflüsse die Sterilität hervorgerufen haben. Eine Lösung der Frage wäre 

 möglich bei Varietäten der Eßbananen, bei denen Samen mit Pollen derselben 

 Varietät erzeugt werden können. Schüepp. 



758) Heald, F. D. and Gardner, M. W*, Longevity of Pycnospores of 

 the Chestnut-Blight Fungus. In: Journ. Agr. Research, Vol. II, Nr. 1, S. 67 

 bis 75, 1914. 



Two sets of tests were made on the longevity of pycnospores of the chest- 

 nut-blight fungus. The field tests show that the pycnospores are to ä consider- 

 able degree resistant to desiccation in soil in the field and that a large number 

 may retain their viability during a period of 2 to 13 days of dry weather. In 

 the indoor tests, where the period of drying could be prolonged at will, more 

 conclusive results were secured. In each sample it is seen that, with some irre- 

 gularities, there is a gradual decrease in the number of viable spores as the pe- 

 riod of desiccation is prolonged. In every case except one a large number of 

 spores survived two months of desiccation and that in 5 out of the 12 samples 

 not all of the spores had succumbed after three months of drying. The longe- 

 vity limit varies from 54 to 119 days, the average beiug 81 days. At the end 

 of periods of desiccation ranging from 12 days for some samples to 149 days 

 for others no viable spores were found. The conclusiveness of these final tests 

 is enhanced by the fact that relatively larger quantities of inoculative material 

 were used in the cultures. These results suggest that viable pycnospores are 

 constantly present in the soil beneath infected trees, since each succeeding rain 

 replenishes the supply. Under normal conditions there would hardly be a period 

 of drought sufficiently extended to destroy all of the enormous number washed 

 into the soil. The fact that a large percentage of the pycnospores which are 

 washed into the soil withstand two to three months of drying has an interesting 

 bearing upon certain phases of the problem of dissemination of the chestnut 

 bark disease and affords at least three possibilities for conjecture. First, it shows 

 that pycnospores will resist the degree of drying necessary to reduce the soil to 

 a condition in which it might be easily pulverized and blown about as dust. In 

 the second place, a means is presented whereby pycnospores might be trans- 

 ported in mud dried on insects, on the feet of birds, squirrels, and other animals, 

 and even the shoes of man. Finally, the results of these tests present the possi- 

 bility of the transportation of pycnospores in the soil adhering to the stems and 

 roots of chestnut nui'sery stock during shipment. Such nursery stock might be 

 uninfected and hence pass inspection as free from disease, the spores having 

 been washed into the soil from diseased parts pruned from the specimens before 

 shipment or from diseased plants which were adjacent to the healthy specimens 



