POSSIBLE SOURCE OF LEAF-SPOT DISEASE OF CELERY. 477 



it can be killed without adversely influencing the vitaHty of the " seed " 

 itself. 



The spread of the disease from place to place is thus satisfactorily 

 accounted for, and means for preventing this have been discovered, 

 but it may not be superfluous to point out that when once the disease 

 has obtained a foothold in a garden or field its reappearance in 

 subsequent seasons may occur even if unaffected or disinfected seed 

 be used. The fructifications containing the spores of the fungus are 

 produced often in enormous abundance on the diseased foliage of 

 celery plants, and can exist uninjured on the decayed remains of such 

 foHage over winter. Unless such decayed remains are promptly 

 destroyed by burning, they constitute a source from which the disease 

 may arise in the following season. 



To combat this disease, therefore, three modes of attack must be 

 employed. 



1. All celery seeds should be examined by a competent mycologist, 

 and if necessary they should be treated with an appropriate germicide. 

 The onus of providing disease-free seed should, of course, not be placed 

 on the gardener. He should thrust it on the seed merchant and he 

 in turn upon the seed-grower. 



2. If the disease appears it should be kept in check by spraying 

 the plants with Bordeaux mixture, in a somewhat similar manner to 

 that adopted for checking potato bhght. 



3. All diseased portions of the plants should be most carefully 

 collected and burned, and in no circumstances should they be 

 allowed to remain in or on the soil, or to reach the manure or compost 

 heap. 



There is, however, a further possible source of infection, namely 

 by transference from plants other than cultivated celery. The same 

 fungus, it seems, is found, though in the British Isles apparently only 

 rarely, on parsley. It is not unHkely, although definite proof by 

 means of infection experiments has, so far as I am aware, not yet 

 been brought forward, that the celery leaf-spot disease may be 

 contracted from affected parsley. 



If the same fungus occurs on parsley it is not unreasonable to 

 suppose that it may be found on other plants belonging to the family 

 Umbelliferae, and in particular on wild celery. In this connexion the 

 following passages, quoted from Mr. Chittenden's paper in this 

 Journal already alluded to, are of interest. DeaHng with the distribu- 

 tion of the fungus on celery, he says : "A curious and possibly 

 significant fact is that there are apparently no records whatever of 

 the fungus attacking wild plants. The celery occurs wild in marshes 

 over a large area in Europe, North Africa, Western Asia, and North- 

 West India, but the disease seems to have been spread with cultivated 

 celery and not from the wild plants to cultivated ones, as so many 

 fungi have done." 



Further on he says : " As already pointed out, there are no records 

 of the occurrence of the fungus on wild celery. It must, however, be 



