PLANTS IN THEIR RELATION TO DISEASE. G5 



feet below the others. They flow into a ditch, where this 

 brook percolates down through, that has planking on the 

 sides and bottom, and that water is carried off, supposed to 

 be purified, into Lake Cochituate. 



The CiiAiRMAX. I have now the pleasure of introducing 

 Prof. D. P. Penhallow, who Avas connected with the Agri- 

 cultural College in Japan at its foundation, and is now a 

 professor at McGill College, Montreal. 



PLANTS IN THEIR RELATION TO DISEASE. 



BY. rUOF. D. P. PENHALLOW. 



[The manuscript of the lecture was not received in time to be printed.] 



The Chairman. If any one has any question to ask 

 Prof. Penhallow there is now an opportunity. 



Mr. Phillips. I would like to ask Professor Penhallow 

 how to cure the pear blight. 



Prof. Penhallow. We do not 'pretend to cure it yet, 

 but we hope we have some light upon it. Dr. Goessmann, 

 some time since, found that sulphate of potash was the most 

 effective salt which could be applied. I have submitted trees 

 to treatment involving the use of sulphate of potash as a 

 special fertilizer, and phosphates as a general food for build- 

 ing up the constitution, with a considerable degree of suc- 

 cess, which would seem to give us hope that we may be on 

 the right track. 



Mr. Ware, of Marblehead. I would like to ask the 

 cause of pear blight, and in what condition is the tree most 

 subject to blight; whether in a state of vigorous growth, 

 which would be induced by high cultivation, or a less vigor- 

 ous growth, that would naturally be developed when land 

 is in grass, but not under active cultivation? 



Prof. Peniialloav. Pear blight in its mode of develop- 

 ment is so complicated, that we have not yet been able to 

 arrive at a conclusion which would enable us to determine 

 what maybe its precise cause. Certain farmers, whose judg- 

 ment is very good in such matters, have assured me that 

 their trees have been in the best condition when they were 

 growing in grass land ; and others have said that that is the 

 worst possible condition in which they could be grown. I have 

 seen trees where the results have been favorable and unfa- 



