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principal vegetative functions of the potato-plant are carried on. No 

 one who has witnessed this can hesitate to admit that very great de- 

 rangement of the functions must arise from such interference on the 

 part of the fungus, and the consequence may have been a diseased 

 action upon the tubers then in the course of formation. Mr. Berkeley 

 accounts for the presence of the fungus upon the plants while as yet 

 in a healthy state. I quite agree with him in the opinion that " as far 

 as the aerial portions of the plant are concerned, the Botrytis is the 

 immediate cause of destruction in all those cases where the potato 

 herbage was not cut down by unseasonable frost" — that the disease 

 commences in the leaves, and that the potato-herbage was very gene- 

 rally infested with the Botrytis. I admit also, that " it is not the habit 

 of the allied species of fungi to prey on decayed or decaying mat- 

 ter, but to produce decay," but I do not admit the conclusion that 

 " the plant becomes unliealthy in consequence of the presence of the 

 mould which feeds upon its juices and prevents the elaboration of nu- 

 tritive sap in the leaves." That an injurious effect does ensue under 

 the action of the fungus, I admit, but then 1 consider that a previous- 

 ly unhealthy condition of the potato-plant (whether from atmospheric 

 causes or otherwise) may be a necessary condition for the establish- 

 ment of the parasitic fungus upon the potato-plants. 



Until the disease is better defined and ascertained, and its history 

 better known in reference to former years, I am induced to consider 

 that the atmospheric influences of the past season were quite sufficient 

 to produce a diseased state of the potato-plants before the Botrytis 

 attacked them. With Dr. Montagne, I however admit the intimate 

 connexion of the disease with parasitic fungi. 



Dr. Andrew Ure, in the 'Lancet' for January, has given a very sin- 

 gular view of the disease : he says, " This vegetable distemper, like 

 that of the cholera, while general in its diffusion, is determined to par- 

 ticular localities and plants by certain predisposing causes; yet is 

 independent of these, having occurred in many regions where such 

 causes did not materially operate. Whether it will recur no human 

 being can predict." Certainly a disease of such a capricious charac- 

 ter as this is represented to be, must baffle every attempt at prognos- 

 tication. We are principally concerned at present to ascertain what 

 are the predisposing causes. In this neighbourhood the potato-her- 

 bage was certainly killed off by frost, which also destroyed the Dah- 

 lias and scorched the Fuchsias of the gardens round Warrington ; but 

 T am not by any means disposed to deny that the Botrytis was, until 

 then, exerting an injurious action upon the crops. I believe that the 



