On the Cultivated Potato. 
285 
lived on the man whose biog^raphy we desire but which has 
never been written. M. de Bcarj and Mr. Worthington Smith 
are not agreed on some essential points ; * I must say I read 
only the other day the evidence before the Committee of the 
Commons in 1880 of the last-named authority with particular 
pleasure. I can afford to treat the fungoid theory lightly, 
because the responsibility is not with me ; the grain of that 
theory, as will be seen in the sequel, the Commons Committee 
has sufficiently threshed out, weighed, and garnered : upon the 
scientific evidence, the Committee report that the nature of the 
potato-disease of 1845 consists in the growth on or in the plant 
of the fungus named Peronospora infestans. 
M. de Bary is full of admirable candour ; over and over again 
as regards these fungoid experiments he warns us against self- 
deception ; he says of his Pythium vexans experiment, in which 
he had been working with tainted material, " without the 
greatest care one may be led into great error, and in this direc- 
tion criticism ought to be applied" [p. 259] ; again [p. 267], 
" the negative result caused me to doubt whether my previous 
explanation could hold good in the open field." With such 
complicated materials as living plants, with other fungi, namely, 
amongst others, spicaria \ and Fusisporium, besides animal in- 
fusoria all about, and with sickly tubers, spores, and bell- 
glasses, "miniature gardens" and boxes without bottoms, 
" garden soils " and flower-pots all over the place, error could 
easily creep in and results very readily get mixed. M. de 
Bary's modestly-related researches, followed in many cases by 
purely negative results, have not touched to settle the ques- 
tions, amongst others, of Hibernation and Host-plants. It is 
not so much M. de Bary himself as the school of De Bary 
which has dogmatically laid down this somewhat unfructifying 
proposition — there is no dispute as to the cause — all idea of- 
other causes of the potato-disease of 1845 are excluded, because 
De Bary inoculated healthy plants ; inoculation is defined as 
the introduction of a poison into a wound. Logically, this is 
drawing a very wide conclusion from very narrow premisses. 
If during eight years this experiment has not been repeated 
and confirmed by many persons in many places under varying 
and normal circumstances, I have, by way of argument, a 
perfect right to do so, and would very courteously question, 
* The principal point at issue between the two is that De Bary thought what 
he called Pythium vexans was a distinct organism, whilst Smith regarded it as a 
dimorphic form of the Ferojwsjiora. — J. G. B. 
t Spiearia is a genus of moulds, but it has nothing special to do with potatoea. 
The three potato-pests arf: Botrytis or Peronospora infcstam, Fusiporium solani, 
and Sowsporium scabies. — J. G. B. 
