236 ASCOMYCETES. 



" Casting " or premature withering and fall of needles is not 

 uncommon in nurseries of pine. Amongst some of the causes 

 which lead to this are:^ frost, drought in winter on frozen 

 ground free from snow, drought in summer on dry soil, over- 

 crowding of plants in the nursery, and, finally, a "casting" due 

 to fungi. 



The symptoms in the case of the present fungus are spotting 

 and withering of the needles, due to the presence of a mycelium 

 inside them. In early autumn, or later if the weather he dry, 

 the pycnidia (spermogonia) make their appearance as little black 

 prominences containing tiny .unicellular conidia. The flat black 

 apothecia are developed later, on first-year seedlings during 

 the first autumn, or on older plants during the second autumn, 

 but generally they do not appear till the third year ; they 

 reach maturity on needles still attached, more frequently, how- 

 ever, on fallen ones. Dehiscence consists in the rupture of 

 their delicate black covering, through pressure of the swelling 

 asci and spores in damp weather. The asci are club-shaped 

 and contain eight thread-like one-celled spores, more or less 

 twisted round one another. The septate paraphyses have a 

 slightly bent point. 



Diseased seedlings die off, generally without loss of their 

 leaves. Two-year-old and older plants are always weakened by 

 the loss of needles, and in severe cases are killed. On such, 

 the " casting " or sudden fall of all infected spurs and needles 

 takes place in spring. The mycelium often makes its way 

 from the needles into the tissues of the shoot, and then death 

 of the whole plant soon follows. Disease of the needles of 

 old trees may also occur without inflicting much damage on 

 the trees themselves; they will, however, act as centres for 

 infection of younger plants, particularly those in seed-beds 

 and nurseries in the vicinity. 



Confirmatory experiments on infection of pines by this 

 Zophodermium were first carried out by Prantl, later by Tursky 

 and Hartig. 



The disease appears with such virulence and frequency, that 



the whole of the young pine-growth of a locality may be 



destroyed. It is thus a most dangerous disease, and at the 



same time one difficult to combat. Districts which have 



^Holzner gives a summary of numerous theories on leaf-cast, (Freising, 1877). 



