ON THE LYCOPERDON CANCELLATUM. 219 



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 another : 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 mildew of wheat, 

 and other plants, from a diseased to a healthy subject, in the same 

 season, that I had not any expectation of succeeding in an attempt of 

 that kind ; but I thought it not improbable, that I might succeed in 

 communicating this disease to seedling plants of the pear-tree, having 

 long ago satisfied myself that the species of fungus, which forms the 

 mildew of wheat, always rises from the root of the plant. 



I have many years been in the habit of raising annually pear-trees 

 from seeds, with the hope and expectation of obtaining new and hardy 

 varieties for the dessert in winter ; which may succeed without the pro- 

 tection of a wall ; and as the means I employ to obtain seeds well 

 calculated for my purpose, necessarily cost me a good deal of time and 

 labour, I have always planted them in pots, and in the kind of mould 

 which long experience has pointed out to me as the best. This I have 

 always obtained, at the period of sowing the seeds, in January or 

 February, from the banks of a river at some distance from my garden ; 

 and in this mould my seedling pear-trees always sprang up, and remained 

 during the first season perfectly free from disease. In the spring of 

 1813, a portion of this mould, which I did not want, was intentionally 

 placed very near some hawthorns and pear-trees, upon which the lyco- 

 perdon cancellatum abounded, where it remained till the spring of 1814, 

 when it was put into pots, and new seeds deposited in it. These sprang 

 up as usual, and remained in perfect health till the end of May or begin- 

 ning of June ; when the fungus presented itself upon almost all the first 

 true leaves of the plants, which leaves had composed the plumules of the 

 seeds. 



That the fungus, in this case, rose from the ground, will, I think, 

 scarcely be questioned ; but it is necessary to state, that the seeds were 

 all taken from trees which were not quite free from disease ; and that I 

 saw in the last spring some diseased plants, in a case where every pre- 

 caution, except that of using new pots (which had been my previous 

 custom), had been taken ; and therefore, whilst so little is known respect- 

 ing the habits of plants of this tribe, the preceding facts are not sufficient 



