260 Wisconsin State Horticultueal Societt. 



tors. Others reasoning from analogy as seen in the general princi- 

 ples of reproduction in nature, and especially from the fact that 

 this process is clearly seen in other species of the genus Peronos- 

 pora, as in P. viiacola (grape mildew), and also in the Gysiopus 

 (white rust), which it closely resembles in nearly all other 

 respects, and from the fact that some more enduring germ than 

 any yet known seemed to be necessary to account for the sudden 

 and abundant development of the myriad germs that all at once 

 make their appearance, from season to season, have been led to 

 carefully investigate the winter condition of the fungus, and the 

 observations made tend to confirm the opinion that there is a win- 

 ter or resting spore of the P. infestans and that there are fecunda- 

 tory organs like those iu other forms of fungus growth. The sub- 

 sequent papers by Professor Worthington G. Smith relate to these 

 investigations and their results. Some of the conservatives claim 

 that these observations are not conclusive, because more care was 

 not taken to guard agaiost the growth of other germs in connec- 

 tion with the experiments, but as Professor Smith states, the fact 

 of similar results in the different trials, and the subsequent 

 development of these winter or resting spores into undoubted 

 P. infestans, ought to be conclusive. 



The asexual spores have, as stated by different observers, vari- 

 ous forms of development or germination. In some instances 

 they are but simple spores, containing a single germ. Again, 

 when placed in conditions favorable for growth, they will increase 

 rapidly in size, and at length bursting at the apex will send out 

 an irregular mass of protoplasm, or dust like spores, each par- 

 ticle of which is a living germ which only needs the opportunity 

 to develop into a perfect plant. Yet another form of develop- 

 ment is seen where there is a vigorous growth of the fungus, or 

 where the conidia fall into water, as on a leaf wet with ram or 

 dew. In these conditions they rapidly absorb the water and in- 

 crease in size. The fluid contents of the conidium assumes a 

 granular character and is soon divided into from six to sixteen 

 granules or parts. A short time after this internal division the 

 conidium bursts open and the granules or spores pass out one at 

 a time. Their form is that of a plano-convex lens with obtuse 



