180 On the Lycoperdon cancellatum. 



leaves of different Pear trees, just at the period when the 

 liquid exuded from the spots upon their surfaces, with quick 

 lime and with fresh wood 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. 



As the existence of this species of fungus appeared, three 

 years ago, to be confined to my garden and a few Pear trees 

 in its vicinity, and to the Hawthorn in an adjoining hedge 

 (for it attacks the Hawthorn as well as the Pear tree), I then 

 thought that it would be practicable to ascertain decisively 

 the means by which it transfers itself from one tree to ano- 

 ther : and this appeared to me to be an important object ; 

 because the habits of the Lycoperdon cancellatum, and of the 

 fungus which forms the rust or mildew of wheat, are, in 

 many respects, very similar. 



I had so often tried, without success, to transfer the mil- 

 dew of wheat, and other plants, from a diseased to a healthy 



