218 ON THE LYCOPERDON CANCELLATUM. 



globular bodies I concluded to be seeds of a species of fungus ; but as a 

 few only of the leaves of my trees were affected, and no very injurious 

 effects were visible, I did not take any measures to prevent their disper- 

 sion over my garden. 



I did not, however, long remain ignorant of the formidable nature 

 of my new enemy ; for within two years, every pear-tree in my garden 

 became in some degree diseased. The leaves only, at first, appeared to 

 be injured ; but the disease soon extended itself to the annual branches, 

 in many protuberant yellow spots, beneath which the bark was found to 

 have acquired a bright yellow colour : and as far as this colour extended, 

 the bark, and the wood beneath it invariably perished, either in the same 

 or following season, leaving wounds similar to these inflicted by canker, 

 but less curable. The fruit also became diseased and worthless, and almost 

 all the young shoots, when once attacked, perished in the following 

 winter. These effects were not confined to my garden, but extended 

 to the pear-trees in an orchard which was two hundred yards distant ; 

 and I Ccinnot entertain a doubt, but that the disease was communicated 

 to these by seeds which had been conveyed by the prevalent west winds. 

 I endeavoured, during the summers of 1813 and 1814, to check its 

 progress in my garden, by picking off every diseased leaf ; but I found 

 all my efforts nearly abortive, and 1 have been obliged to destroy the 

 greater part of my pear-trees : those which remain have become annu- 

 ally more diseased, and I fear never can be ultimately preserved, unless 

 a remedy for the disease can be discovered. 



I tried the effect, in the last season, of sprinkling the leaves of 

 different pear-trees, just at the period when eht liquid exuded from 

 the spots upon their surfaces, with quick-lime and fresh w r ood 

 ashes, in which the alkali and lime were in a caustic state ; and with 

 flowers of sulphur. The spots to which the quick-lime and ashes were 

 applied, soon became paler ; but I had not an opportunity of observing 

 the ultimate effect of these substances : for almost all the leaves of the 

 pear-trees upon my walls, in the last season, became covered with black 

 and lifeless spots, and fell off prematurely. Those of a single small 

 standard pear-tree, on which flowers of sulphur had been sprinkled, 

 remained alive till late in the autumn ; and upon these I did not observe 

 the sulphur to operate in any degree, till the period at which the conic 

 processes above-mentioned would have appeared ; but the yellow spots 

 then became black, and perished, without affording seeds ; whence I 

 have reason to hope, that flowers of sulphur will prevent, in some 

 measure at least, the rapid extension of this disease. 



