470 PROTECTION AGAINST FUNGI. 



The club-like asci in the perithecia contain eight 1 -celled and 

 later 2-celled spores. The perithecia ripen at the end of May 

 and the beginning of June. In three weeks from the moment 

 of infection, they produce fresh conidiophores. 



b. Subjects of AttacJc, and Distribution. 



The fungus appears to attack larch of all ages. Dry, 

 breezy localities are less liable to the disease than damp foggy 

 ones. For this reason, larches on mountains, where the 

 summer air is dry, whenever the air is cloudless, are less 

 endangered than those on hills and in lowlands. The season 

 during which the fungus can form conidia is much shorter 

 in mountains than in lowlands. 



The danger is greatest in pure larch woods and in mixed 

 woods of larch and spruce. In the former, the infection is 

 easy, owing to the propinquity of the larch trees ; in the 

 latter, the fallen infected larch needles lie in masses on 

 the spruce branches, where the ascophores can easily infect 

 the larch. A mixture of beech and larch is favourable, as the 

 dense fallen beech leaves hinder the spores from ascending. 



Japanese larch is also attacked. 



In the cold, wet summer of 1894, this disease was so 

 prevalent in Upper Bavaria, that by the beginning of August 

 most of the larch needles had fallen. 



c. Protective Measures. 



i. Grow larch in suitable localities. 



ii. Mix larch with beech and not with spruce. 



Melampsora Trcmulae, Tul., also named Caeoma laricis, Hrtg., 

 p. 447 (Fig. 238, p. 486), also induces larch needle-cast. Aspen 

 should not, therefore, be grown in larch woods. 



23. Trichosphaeria parasitica, E. Hrtg. 

 a. Description and mode of Attack. 



The fine colourless mycelium of this fungus covers the 

 twigs of the silver-fir down to the buds, especially on their 

 under surface, and spreads to the lower needles, whilst the 

 shorter upper needles usually escape infection. The mycelium 



