CHAP. XITL] Fungoid Diseases of Trees 305 



groundsel (Senetio), the spores from which scatter in the follow- 

 ing spring, spreading abroad the germs of the Pine needle- 

 rust and the Pine canker ; hence it is advisable to remove 

 groundsel before it flowers in April. Aeddium abietinum has its 

 Teleutospore form as Chrysomyxa rhododendri on rhododen- 

 drons, and Aeddium columnare its change of generation with 

 the Calyptospora Goeppertiana on cranberries. What form is 

 assumed by the aecidial spores of Aeddium elatinum, or on 

 what plant they occur, has not yet been discovered. 



Caeoma pinitorquum becomes Melampsora tremulae on 

 Aspen foliage, hence Aspen should be cut out of Pine woods 

 to prevent the development of the Pine-shoot fungus. The 

 Larch blight, Caeoma larids^ has also its Melampsora form on 

 Aspen foliage. 



M. Betulina on Birch probably stands in relation with some 

 form of Caeoma. Melampsora Hartigii, the Willow-rust, has 

 first its Uredo-form, Uredo salids, and then its Teleuto-form, 

 Caeoma ribesii^ on gooseberries and raspberries; but this last 

 form is not absolutely necessary for its regeneration. Melam- 

 psora salidna on the Goat-willow similarly becomes Caeoma 

 evonymi on the Spindle-tree. 



Prevention and Cure of Fungoid Diseases in Trees. 



The great sylvicultural authority on this matter, Professor 

 R. Hartig, expresses the following opinions 1 : 



' The best prophylactic measures against the outbreak and spread of 

 epidemics is the formation of mixed woods. Subterraneous and super- 

 terrene infections are best obviated when each tree is, as it were, isolated 

 by neighbours of different species. A change in the species of tree may 

 even seem advisable, under certain circumstances, on soils which have 

 been taken possession of by root-parasites, or which contain Teleuto- 

 spores retaining their vitality for many years. Avoidance of the conveyance 

 of fungus spores by men and animals is recommended, especially during 

 operations in young tree-forest. The therapeutic measures adaptable after 

 any outbreak of fungoid disease occasioned by root-parasites consist 



1 Op. cit., pp 55, 56. 

 X < 



