Il8 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



of the Cytospora disease, however, the leaves do not shrivel, 

 and remain pale brown in colour, and, as a rule, the whole of 

 the leaves of the infected portion of the shoot are attacked. 



Measures for the prevention of the disease are, unfortunately, 

 somewhat difficult. Where young trees are severely infected 

 these should be removed and burnt. In the case of larger 

 trees, especially where they are isolated or grown for decorative 

 purposes, the infected branches should be cut off and burnt 

 as soon as the disease appears. The fungus appears to be 

 confined at present to areas in the south and west of Scotland, 

 and, if the measures recommended are promptly carried out, 

 it is possible that the spread of the disease may be checked. 



Planting of the common silver fir has now to a large extent 

 been discontinued, but Abies grandis has been grown more 

 extensively in the last few years. The disease has not been 

 found up to the present on this species, but it is possible that 

 it may also become attacked. Experience has shown that the 

 spread of disease in pure plantations is more rapid than in those 

 in which the species are mixed. In view of the possibility 

 of infection of Abies grandis by Rehiniellopsis and other fungi, 

 it is suggested that where this species is utilised, it should 

 not be grown extensively in pure plantations. 



EXPLANATION OF PLATES. 

 Plate IV. 

 Fig. I. Twig oi Abies pectinata, showing diseased leaves. 

 Fig. 2. Apex of leading shoot of A. pectinata ; the bud has been killed, 



and at (a) fructifications can be seen as dark-coloured dots on 



the infected leaves. Groups of eggs and mature insects of 



Chermes are seen at {b). 

 Fig. 3. Twig of ^. nobilis, showing diseased leaves soon after infection. 

 Fig. 4. Twig of A. nobilis, showing diseased leaves five months after 



infection. 

 Fig. 5. Transverse section of leaf of A. pectinata, showing perithecia. 



Plate V. 

 Fig. 6. A perithecium, with asci and spores. x 160. 

 Fig. 7. Transverse section of leaf of A. pectinata^ showing hyphae in the 



tissues. X 150. 

 Fig 8 Transverse section of leaf, showing perithecium and asci. 

 Fig. 9. An ascus, containing ascospores. x Soo. 



