22 I'LANT DISEASES AND FUNC.I. 



and destroyed. Upon inquiry it was found that all the plants raised 

 by the gardener's friend were also diseased in the same manner. The 

 only inference to be derived from these facts is that the disease was 

 latent in the seeds of the diseased plants, and that it was a clear case 

 of hereditary transmission. His own plants, raised from clean seed, 

 showed no trace of disease, although growing in close proximity to 

 diseased plants. 



Another instance may be cited in support of this view. " Some 

 remarkable phenomena occurred in a garden near London, where 

 all the plants of Pyracantha, arising from particular seed, were more 

 or less completely destroyed by the same species of Fusicladium 

 which injures the pear trees. [The cause of the American "apple 

 scab."] The plants were raised from Russian seeds, about four or 

 five years previously. They first appeared to be blighted in the 

 year preceding this report, but inconsiderably. In the following 

 year they were nearly all killed. The old shoots were black with the 

 spores, the leaves crumpled and withered, and the late shoots and 

 leaves were about to break out as their predecessors. The seedling 

 bushes were growing in heavy land, well drained, but the disease 

 was confined to them. Old bushes of Pyracantha in the same 

 places were perfectly clean." ^ 



Not only are plant diseases hereditary, as are some diseases in 

 the human subject, but they appear to be analogous also in their 

 epidemical character. Many years since the Rev. M. J. Berkeley 

 alluded to this subject in the following terms : — " There is some- 

 thing extremely capricious in the attacks of these diseases amongst 

 plants, exactly as is the case with infectious maladies amongst our- 

 selves. One is taken and another left without our being able to 

 account for it ; nor is it probable that we shall ever penetrate these 

 mysteries, which baffle all our efforts, and remind us of our true 

 position in the scale of intelligent beings. A perennial plant, or 

 tree, once attacked by parasites, seldom gets perfectly free from the 

 disease, and there may be a greater analogy in the peculiar liability 

 of certain constitutions to the recurrence of such maladies as 

 influenza, than, in fact, in the present state of our knowledge as 

 to the cause of disease we should be willing to allow." 



The manner in which some of the most notable of fungus 

 diseases have appeared affords remarkable coincidences with the 

 spread of such human epidemics as cholera and influenza. The 



4 " Gardener's Chronicle." October 28th, 1848. 



