DETAILED ACCOUNT OF SPECIFIC PLANT DISEASES 519 



tucket only a few host leaves were left on a row of garden hollyhocks, 

 all of the other leaves having fallen off. The sori consist of light- 

 colored teliospores which are two-celled and measure 17 to 241J, by 35 to 

 63M (Fig. 187). 



Bordeaux mixture (4-3-50) has been found efficient, as a spray, in 

 controlling the hollyhock rust. Others recommend sponging the dis- 

 eased parts with permanganate of potash, two tablespoonfuls of 

 saturated solution diluted with one quart of water. 



Larch (Larix spp.) 



Canker {Dasyscypha Willkommii, Hartig). — The life history of this 

 destructive fungus of larch trees has been studied by German plant 

 pathologists, so that it is pretty well known. In the moist, marsh 

 meadows in the mountains of Europe where the larch has been planted 

 in pure forests, the fungus has been frequent in past years. The 

 mycelium attacks the bast elements of the stem and its insidious char- 

 acter is manifested in the death of the bark, which peels off. Pro- 

 nounced cankers soon develop and the fungus lives perennially in the 

 tree spreading rapidly when the larch tree is comparatively inactive, 

 viz., autumn and winter. The diseased area, represented by wounded 

 tissue, may heal over during the growing season, but when the fungus 

 regains its activity the disease progresses until the branch is com- 

 pletely girdled and its terminal part dies. 



Creamy white stromatic tufts appear, where the bark has been killed 

 and on this superficial mycelium minute conidiophores arise, which 

 bear simple hyaline conidiospores. As these probably do not germinate 

 they have no influence in the spread of the canker. Short-stalked 

 apothecia may appear on the canker areas later in the year. They 

 are somewhat yellow on the outer surface and orange within. The 

 cylindric asci (i20;u by gn) bear light ovoidal, unicellular ascospores. 

 Filiform paraphyses are found between the asci. No efficient remedial 

 measures are known. 



Dry-rot (Trametes pini (Brot Fr.). — This fungus is very common 

 in the forests of New England, Canada and Newfoundland. It grows 

 on nearly all coniferous trees; white pine, red spruce, white spruce, 

 hemlock, balsam fir and larch attacking the living trees after they 

 begin to form heartwood. In the tamarack, or larch, the decay goes 



