PREVENTING DISEASE 179 



receive special attention in the matter of an 

 annual examination, and especially is this the 

 case with such brittle-branched trees as the 

 elm and poplar, large limbs of which frequently 

 snap across without the slightest warning and 

 to the danger of visitors. No cursory examina- 

 tion of such trees should be allowed, but 

 every part of the stem and heavier branches 

 carefully gone over, in order to find out where 

 weak spots exist. 



It occasionally happens that during warm, 

 still weather heavy limbs of such trees as the 

 poplar and elm snap over without the slightest 

 warning, and often to the danger of those who 

 may be present beneath their shade. Several 

 cases of this kind have occurred of late, and 

 in two instances at least with fatal results. 

 The reasons for this sudden snapping of 

 branches are : (i) disease or injury ; (2) dis- 

 position and size of branch ; (3) the extra 

 weight of foliage during the growing season ; 

 and (4) the brittleness of the timber caused by 

 the flow of sap. In some parks and gardens 

 the Royal parks in particular an annual 

 examination of the trees is made, and all heavy 



