220 ON THE LYCOPERDON CANCELLATUM. 



to support a decision, that the source of the disease might not have been 

 in the seeds themselves. For as the fructification is probably everything 

 which is seen of this, and many other parasitical fungous plants, the 

 plant may extend in minute filaments through the whole body of the tree 

 which supports it ; and it appears in this view of the subject possible, 

 that these slender filaments may extend into the seeds. The following 

 circumstances, however, militate strongly in opposition to this conclusion. 

 A great number of seedling pear-trees, which were very much diseased, 

 were removed, in the last spring, from my garden to a distant situation, 

 after having had their roots and stems carefully and repeatedly washed, 

 and brushed, so as to remove from them every particle of the mould in 

 which they had previously grown ; and upon these not a vestige of 

 disease has since appeared. Grafts also, which were formed of parts of 

 diseased trees, have in all cases produced perfectly healthy foliage, even 

 when inserted into the branches of other diseased trees ; which circum- 

 stance I think interesting, because it tends to point out a further 

 apparent similarity in the habits of this species of fungus, and that which 

 forms the mildew of wheat : which ceases to vegetate as soon as the 

 straw is severed from its roots, though that remains for some time green 

 and living : whence arises the advantage of cutting mildewed crops of 

 wheat in an immature state. Further experience can, however, alone 

 decide these points : and the only inference I wish to draw from the facts 

 I have stated is, that the lycoperdon cancellatum is capable, under 

 certain circumstances, of being transferred from one plant to another in 

 its vicinity, by means of its seeds. 



I observed this disease, in the last summer, upon a few of the leaves 

 of several pear-trees in the vicinity of London ; and I fear that the 

 fungus which occasions it is an imported species, that is likely to increase 

 in our climate, and to become, in some situations at least, extremely 

 injurious to one of the most valuable of our fruit-trees. I have met with 

 several intelligent gardeners who, at first view, thought they had observed 

 this disease some years ago ; but on further inspecting its habits and 

 injurious effects, they have always changed their opinion. 



The enormous injury which the crops of wheat sustained in the year 

 1814 and other seasons, by mildew, attaches a great degree of interest 

 to the investigation of the habits of parasitical plants of this tribe ; and 

 the similarity of habits of the mildew of wheat, and of the lycoperdon 

 cancellatum, renders it probable that both are propagated in the same 

 manner. I therefore venture to hope that the foregoing account, though 

 very imperfect, of the apparent mode of propagation of the latter plant, 

 may be thought deserving the attention of the Horticultural Society. 



