20 



ON A DISEASE OF THE BEECH CAUSED 

 BY BULGARIA POLYMORPH A WETT. 



By R. J. TABOR, B.Sc, and KATE BARRATT, M.Sc. 



{From the De'partment of Botany of the Imperial College of Science and 



Techno logy, Lo ndon . ) 



(With Plate I.) 



During the last few years, a number of the pollard beech trees at 

 Burnham Beeches have suffered from a disease which has apparently- 

 caused the death of several specimens, and is seriously affecting some 

 others. The symptoms of the disease are very marked. At various 

 points on the surface of the bark a brown liquid exudes which rapidly 

 concentrates to a dark viscous gum^, collecting in gouts near the point 

 of exit and, if in quantity, trickling down to lower levels. The material 

 is partially soluble in water, with the result that in wet weather it is 

 washed down and may be thus distributed over a considerable area 

 of the lower part of the trunk. The effect is very vmsightly and the 

 trees attacked are readily detected (Fig. 1). Frequently the gum 

 provides a medium for the growth of various saprophytes, yeast, bacteria, 

 moulds, etc., and then becomes of a creamy consistency and buff or 

 pinkish in colour. 



The effect on the tree is very serious. The bark from which the gum 

 proceeds is already dead, and since the affected areas are often rapidly 

 extended, the life of the tree may be seriously threatened. 



These pollards are probably some of the oldest beeches in existence. 

 Their life has been prolonged far beyond what is generally regarded as 

 the normal limit of the species by the sj^stematic pollarding, which — 

 as was usual in ancient forestry — was done at such a height as to pro- 

 tect the young shoots from browsing animals. The cessation of cutting, 

 however, permitted the growth of a few of the more favoured shoots 

 and the trees now bear several fine limbs rising £i'om the crown. 



^ This substance has been referred to throughout as gum, though its exact nature has 

 not yet been determined. 



