No. 4.] PLANT DISEASES. 41 



Professor Jones. I can't answer directly, as I am not 

 acquainted with those varieties ; but there are a few varie- 

 ties to-day that will produce some seed balls. I know of 

 none that will produce a great many, but every potato 

 breeder has some that he keeps for that purpose. I can per- 

 haps answer the question in another way. I was impressed 

 in northern Germany with the relative number of seed balls, 

 variety after variety bearing them abundantly ; but where it 

 is a general thing for varieties to have seed balls there, the 

 same varieties as grown at Burlington have ver}^ few. The 

 same thing was true in Scotland and England, seed balls 

 being relatively common. Why is it? I can't positively 

 say, but of course I have my notions. Some say Paris 

 green. If any one wishes to believe that, it is his privilege ; 

 but I don't believe it. What is it, then? I suspect that 

 the principal cause lies in our climatic conditions. The 

 short season has, as already explained, thrown the plant 

 out of its normal physiological balance. Tuber production 

 croAvds upon seed formation ; the plant cannot well do ])oth 

 at the same time, and we have selected these varieties which 

 throw theu' reproductive forces most strongly to tuber forma- 

 tion. Moreover, I think that the larger amount of bright, 

 hot, dr}'^ weather, characteristic of our climate as compared 

 with the European, reduces the vitality of the reproductive 

 parts of the blossom. 



Hon. Wm. R. Sessions (of Springfield). Professor 

 Brooks's reference to old varieties of potatoes carries my 

 mind back to when I was a boy. The principal potato raised 

 then was the long, red potato. That was about all that was 

 raised in our section at that time, when I had to ride the 

 horse between the rows. My recollection of that potato is 

 that one end was dry and the other was watery, — in fact, 

 the food was sorted in the potato. Can 3^ou tell what the 

 cause of that was? We don't have it to-day at all, do we? 

 There is no potato raised but what is equally good through- 

 out ; but my recollection now is that in this old variety one 

 end was a poor (juality and the other was better. 



Professor Jones. I will answer the question by putting 

 it in a different way. I will cut this jjotato in two, to illus- 



