86 Mr. A. H. Hassall on the Production of Diseases 



X. — Observations on a Disease j the production of a Fungus ^ oc- 

 curring in the Lettuce and other Vegetables. By Arthur Hill 

 Hassall, Esq. 



The production of diseases through the agency of Fungi, whether 

 in the animal or vegetable fabric, has not hitherto received that 

 degree of consideration to which the frequency of their occur- 

 rence and the importance of the subject so eminently entitle them. 



While walking in the garden this evening, I was particularly 

 struck with the appearance of some of the lettuces contained in 

 a fine bed of that vegetable, several of them having become 

 wrinkled and discoloured, although a few days previously I had 

 especially remarked their healthy and vigorous growth. 



On examining several of the affected plants I found a consi- 

 derable softening of the stem near the ground, and which, my 

 mind having been previously prepared for such a phsenomenon 

 by my investigations respecting the decay of fruit, I did not he- 

 sitate at once to attribute to the action of a fungus, — a conclusion 

 which was confirmed by a microscopic examination of the stem, 

 by which the thalli or root-like filaments of the fungus were de- 

 tected without difficulty. 



In one of my papers on the Decay of Fruit, read before the 

 Microscopical Society of London, I stated that if apples were in- 

 oculated with the thallus or sporules of fungi while still maintain- 

 ing a firm connexion with the parent tree, nevertheless that they 

 became afiected with decay ; and from the result of this experi- 

 ment I concluded that the development of the fungi was the 

 cav^e and not the effect of the decomposition, a fact which I con- 

 ceive to be incontrovertibly established ; and in confirmation of 

 which, if any further evidence were needed, the present example 

 of the independent operation of fungi would afibrd that additional 

 evidence ; for of the healthy condition of the lettuces prior to the 

 attack of the fungi no doubt could be entertained, this being 

 abundantly testified by the appearance of the unafifected plants. 



That this disease is communicable by inoculation in the same 

 way as the similar afiection occurring in fruit I cannot doubt ; I 

 will however make the trial and communicate the result in a note 

 to this paper. 



Were the example which I have now recorded of disease in ve- 

 getables, the product of the operation of fungi, an isolated one, it 

 would still be possessed of considerable interest ; but so far from 

 this being the case, I have not the least hesitation in asserting, 

 that the majority, if not the entire, of culinary as well as orna- 

 mental plants are subject to a similar fatal disorder. Amongst 

 the former class I would particularly mention the following, in 

 all of which I have noticed the peculiar softening observed in the 

 stem of the lettuce : — endive, celery, potatoe, cabbage, pea, bean, 



