238 PLANT DISEASES 



LARCH LEAF RUST 



(^Melampsora laricis, Hartig. 

 = Caeoma laricis, Hartig.) 



The aecidium stage of this fungus forms yellow pustules 

 on the leaves of the larch ; as a result the leaves wither and 

 fall. The branches are not attacked. The uredospore 

 and teleutospore conditions grow on the leaves of poplars 

 {Populus tremula, and P. nigra). 



For reasons that cannot be discussed here, it appears 

 highly probable that this fungus is specifically identical 

 with Melampsora pinitorqua, the slight diflferences observ- 

 able being due to the different host on which the fungus 

 grows. Melampsora betulina also probably belongs to the 

 same category. 



Hartig, Allgem. Forst und Jagd. Zeit. 1885, p. 356. 

 Prillieux, Malad. des Plantes Agric, vol. i. p. 292. 



FLAX RUST 



(^Melampsora lini, Tul.) 



The rust is often very destructive to cultivated flax (Linum 

 usitatissimum), and is widely distributed in Europe ; it also 

 occurs in Australia and the United States. The uredo sori 

 form small orange spots on the stem, leaves, and some- 

 times on the sepals. The teleutospore sori form large, 

 smooth, blackish patches on the stem, sometimes almost 

 covering and blackening it all over. The teleutospores 

 are densely crowded side by side, and are covered by the 

 epidermis of the host. Various other species of Linum 

 are also attacked, and this is important to bear in mind. 



