CHAP, xiii.] Fungoid Diseases of Trees 289 



dormant in the soil. As the mycelium is formed, it spreads 

 throughout the whole stalk as well as within the cotyledons ; 

 whilst numerous hyphae break through the epidermis from 

 within, or force their way through the stomata, and develop 

 into s/>0rangia-bearers. After the detachment of the citron- 

 shaped sporangia their receptacles become prolonged and 

 again form sporangia ; whilst the older ones drop off and 

 either at once germinate, or scatter in all directions the Conidia 

 which they contain. The development of this fungus is so 

 rapid that in rainy weather, and in close, damp situations, new 

 sporangia-bearers are formed within three to four days of the 

 first appearance of infection. Ovispores (pospores] are at the 

 same time formed by the sexual process of fructification. These 

 become incorporated within the soil when the infected parts 

 rot away, and retain germinative power for three to four years, 

 or even longer. When once this fungus establishes itself in 

 nurseries, or in areas being naturally reproduced, it may occa- 

 sion very serious damage, as in addition to infection from 

 ovispores (pospores] that are easily carried from place to place 

 by wind and passing animals, the mycelial filaments produce 

 infection subterraneously by entering into the rootlets and 

 suction-roots of neighbouring seedlings. 



Besides the Beech, the seedlings of Ash, Maple, and Syca- 

 more are most liable to its attacks, as well as those of all 

 conifers, but especially Spruce and Scots Pine. So long as the 

 infection only takes place at the tip of the seedling, recovery is 

 possible ; but where, coming from below, it begins to make its 

 appearance in the stem, the case is hopeless. In consequence 

 of this fungus whole seed-beds covered with rills of coniferous 

 sowings may be killed off even before the germinating seed- 

 lings have made their appearance above the soil. 



Preventive measures include the careful removal of infected 

 seedlings whilst the disease is as yet merely sporadic. Any 

 seed-beds which have been attacked should only be used for 

 the schooling of transplants during the two or three following 



u 



