264 "Wisconsin State Hoeticiiltueal Society. 



this decayed matter by heavy fall rains and pass the winter in the 

 earth or on the surface of the ground, and start into new life as 

 soon as the weather becomes favorable the following season. In 

 the germination or development of these resting spores, the same 

 variety of simple spores, sporidia, zoospores and cellular vesicles 

 producing zoospores are seen, as has been described in the asexual 

 form. In both instances, the more favorable the conditions for 

 the growth of the fungus and the more vigorous its development, 

 the greater the proportion of zoospores produced to the other 

 germinal forms. 



There are many facts connected with the earlier history of this 

 parasite which it would be interesting to consider, but the space 

 alreafly given to the subject is much beyond what was intended, 

 and they must be passed by to consider briefly the relation of the 

 fungus to the disease, viz., whether it is the primal cause or only 

 an attendant result. As already stated, there are different opin- 

 ions on this question. Those who hold it is the original cause of 

 the disease rely mainly on the facts that it is always present where 

 the disease is found, and that the disease can be produced in 

 seemingly healthy plants by the artificial application to them of 

 the germs of the fungu?. But neither of these facts are proof con- 

 clusive, for there are many instances where the fungus is not only 

 present in a germinal form, but even where the germs have so 

 developed as to gain hold of the plant tissues and the usual 

 results do not follow. With such a variety and multitude 

 of germs, such a rapidity of development possible, and such 

 facilities for wide spread dissemination, there can be 

 hardly a season during which each plant in our gardens 

 and fields has not more or less of these germs upon it. If, 

 as Professor Smith states, the wind blowing over an in- 

 fested field on the continent of Europe would bear spores enough 

 to thickly seed every field on the British Isles, where is the immu- 

 nity, if they can produce the disease? Again we have^ from act- 

 ual test, seen proof that inoculation or artificial communication of 

 the fungus does not always, and cannot always, carry the disease, 

 but that the fungus is limited, or dependent in its development 

 by the conditions in which it is placed, and on the condition of 



