480 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



found on the wild celery is identical with that which causes the well- 

 known leaf-spot disease of the cultivated celery, and that the original 

 source of the disease is to be looked for in the parasite occurring on 

 the wild plant. That its effect on the cultivated plant is much more 

 serious than on the wild plant is explainable upon the assumption 

 that through continued cultivation the stamina of the host plant and 

 its power of resisting the attacks of parasites has become weakened. 



I think it hkely that if a thorough search were made for it the 

 fungus would be found on wild celery in other countries, and no doubt 

 it was in one or more of them that the original transference of the 

 fungus from the wild to the cultivated plant took place, and possibly 

 is still taking place. 



There is, of course, the bare possibiHty that the wild celery plants 

 in West Galway may have become infected from cultivated plants, 

 but this, I think, is highly improbable. The colony of plants in 

 question is situated in a damp spot near a tiny inlet of the sea, in a 

 very remote and extremely backward part of the country, and although 

 there are a few peasants' cottages scattered through the district, 

 celery is an unknown vegetable there. For this reason also, and 

 because, as far as I am aware, celery is not grown for seed anywhere 

 in Ireland, I do not think that this country can be looked upon either 

 as the source from which the disease came, or as a centre from which 

 it has been disseminated. 



