I46 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



Plate IV.). In the second, the young tree is attacked a short 

 distance above the ground-level, the outer tissues are killed 

 either on one side only or completely round the stem, and 

 ultimately the whole tree is killed (Plate V.). In both cases a 

 very characteristic feature of the disease is the sudden decrease 

 in diameter in passing from the healthy to the diseased portion 

 of the stem, and this is very marked in the second method of 

 attack described above, where the stem immediately above 

 the diseased portion is abnormally increased in thickness. 

 Numerous resin blisters are developed on the stem both above 

 and below the point of attack (Photos 1 and 3), and after these 

 have burst the whitish patches of dried resin are very obvious. 



Some time after the stem is attacked, minute black fungus 

 fructifications appear in large numbers on the dead portion, and 

 in some cases on the dead leaves (Photo 2). These are at first 

 covered, but are later on exposed by the splitting of the bark 

 and finally project slightly above the surface. They contain 

 very minute spores which in damp weather exude from the 

 fructifications in mucilaginous filaments (Plate V., Fig. 4, a), or 

 masses of whitish translucent appearance (Fig. 4, b, c). 



It was at first believed that the disease is caused by the 

 fungus Phoma abietina, first described by Hartig in Germany 

 in 1889 l as a parasite of the silver fir, on which it produces 

 effects closely similar to those described above. This fungus 

 has been stated by Bohm 2 to be the cause of a serious disease 

 of the Douglas fir in Germany. It has also been recorded from 

 France on the silver fir 3 and on a considerable number of 

 different conifers in Denmark 4 . A careful examination of the 

 Scottish specimens, however, shows that the fungus present 

 differs from Phoma abietina, Hartig, in the shape and size of the 

 spores and in the occurrence of a second kind of spore which 

 has not been discovered in the fungus present on the silver fir. 

 It also differs from Phoma pithya, Sacc, a species which has 

 been confused with Phoma abietina but which is distinguished 

 from the latter by the absence of definite sporophores. It is 

 therefore proposed to give the name Phomopsis Pseudotsugae to 



1 Hartig, Lehrbuch d. Batimkrankheiten, 1889, p. 124. 



2 Bohm, Zeitschr. f. Forst- u. Jagd-wesen, 1896, p. 154. 



3 Prillieux et Delacroix, Sur deux Parasites du Sapin pectine, etc. Bull, de 

 la soc. mycologique de France, Tom. VI., 1890, p. 174-178. 



4 Lind, Danish Fungi, Copenhagen, 1913, p. 421. 



