EXPERIMENT STATION BULLETINS. 577 



Hosts. 



So far as the writer has been able to discover by a careful survey of the 

 literature on the subject, this disease has been reported only on celery and 

 celeriac (Apium gravcolens L.). Other Phomas have been reported on species 

 of the Umbelliferae, but in many cases the available descriptions are too 

 meager to admit of satisfactory comparison with the one on celery. It is, 

 of course, entirely possible that this organism may have been reported on 

 other species of plants. The genus. Phoma embraces so many little-known 

 forms, with present descriptions so inadequate, that, until a more compre- 

 hensive study of the genus is made, it will be impossible to determine the 

 validity and host range of many of the parasitic species. 



Inoculation experiments leave no doubt as to the ability of the fungus to 

 attack plants other than celery. Its potentialities along this line have been 

 tested by inoculation of a number of species of the Umbelliferae family with 

 pure cultures of the causal organism. 



Plants, nearly related to celery and of economic importance, were inocu- 

 lated with pure cultures of the pathogen, under conditions very favorable 

 to the production of the disease on celery. Inoculation of carrot (Daucus 

 carota) produced black, sunken spots on the roots and a kiUing of the outer 

 leaves. Pycnidia were found scattered over the diseased parts. (PL IV. 

 Fig. a). 



Parsnip (Pastinaca saliva), while it is by no means immune, seems to be 

 less susceptible than carrot. The region of invasion was largely confined 

 to the upper part of the root and to the base of the leaf stalks. The diseased 

 parts were typically dark broAvn or black. On the root the epidermis was 

 broken and the underlying tissue invaded, which resulted in a "cankered" 

 area. Invasion was very slow and the damage slight, except as the diseased 

 spots disfigured the roots. (PL IV. Figs, b and d). 



Under greenhouse conditions Moss-Curled parsley {Carum 'petroselinum) 

 and celery seem to be equally susceptible to attack of the fungus. Young 

 plants were killed by being rotted off at the base and older plants were sev- 

 erly attacked, showing signs similar to those on celery. Plate IV, Fig. c. 

 shows a typical plant of a series of inoculations. The black crown is char- 

 acteristic. Pycnidia of the pathogen were produced upon all diseased parts. 

 Although it has not been reported, it would not be surprising to find this 

 disease doing damage to parsley under field conditions, particularly in truck- 

 ing and seed-producing districts where celery and parsley are grown exten- 

 sively, with little or no rotation with other crops. 



The attacks of the fungus on caraway {Carum carvi) were very weak. A 

 few leaves were killed by basal invasion but the region of attack is usually 

 limited. Poison hemlock, {Conium maculatum) and dill {Anethum graveolens) 

 have failed to show any lesions in spite of heavy inoculation with mycelium 

 and spores. 



Signs of the Disease. 



GENERAL. 



Cases of mild infection are often impossible to detect on celery, unless 

 the plants are removed from the soil and examined for dark discolorations. 

 Above ground, the first indication of this disease is the dying of a few outer 

 leaves. Often one or two withered leaves lying on the ground, but still 



