GROWTH OF PARASITIC FUNGI. 



animal and vegetable worlds, the same law appears to prevail in both, that an unhealthy 

 state of the larger plant as well as of the larger animal is the essential condition required 

 for the attack and increase of parasites. " The different species of minute insects," ob- 

 serves Mr. Knight, " which feed upon the bodies of our domestic cattle, are scarcely ever 

 seen, and never injurious so long as the larger animals retain their health and vigor; but 

 M'hcn these become reduced by famine or disease, the insects multiply with enormous 

 rapidity, and though they are at first only symptomatic of disease, they ultimately become 

 the chief and primary cause. The reciprocal action of the larger plant and the mildew, 

 upon each other, may be somewhat similar." (Knight's Phys. and Ilort. papers, p. 

 208.) 



I apprehend no further remarks are needed to prove that this is, as you observe, an 

 important subject of investigation, and I would suggest in conclusion, whether some Hor- 

 ticultural Society, or the Poraological Congress would not do well by instituting a search- 

 ing and systematic inquiry with a view to ascertain what are the causes which lead to at- 

 tacks of fungi, and by what means they can be prevented or modified. It is well to re- 

 ward the successful improver of the pear and other fruits as our Horticultural Societies 

 now do; but how much greater would be the service rendered to horticulture, how much 

 more profitably Avould be the money expended, if a means could be discovered which 

 would enable us to grow in a healthy condition, those varieties we already possess, or 

 may hereafter obtain.'' If the inquiry should be confined to the pear alone; the first steps 

 to be taken would be to determine the name of the fungi. A few fresh infected leaves her- 

 metically sealed in a light tin case might be transmitted by post to the first authority ou 

 these plants in this country, and to two or three distinguished cryptogamic botanists of 

 Europe — say the Rev. M. J. Berkeley of England, Professor Morren of Belgium, or Dr. 

 Montague of France, not only with a view to ascertain the name of the parasite, but 

 whether it exists in Europe, and if any means are there known to prevent its development 

 or diminish it power. A plain and accurate description of the disease should then be 

 drawn up, and distributed with a series of inquiries, in different parts of the states to 

 individuals likely to afford useful and accurate information. The returns would show the 

 geographical limits of the disease, the period of its development and its intensity in differ- 

 ent parts. I append a few inquiries which have occurred to me. 



1. Has this disease been observed by you in the locality where you now reside, and if 

 so, how long has it been experienced.'' 



2. AVhen once developed has it ever entirely disappeared, and under what circum- 

 stances.' 



3. Are seedlings more liable to be attacked than grafted varieties.' 



4. Among grafted varieties do any uniformly offer greater resistance to the disease than 

 others ? 



5. "What is the character of the soil of your orchard or nursery, and if there is any 

 difference in the quality, texture, moisture or dryness of the soil, are trees more free from 

 disease in one part than another, and if so, which.' 



6. State the position of j'our orchard, whether on low ground or on the side of a hill, 

 and whether you have observed in the same locality trees to be more exempt from disease 

 in one position than another.' 



7. Are teees growing in damp shady places more affected than those in more exposed 

 situations? 



Does difference of aspect, as the north or south side of a hill, make any difference.' 

 Are trees growing in grass less affected than those in cultivated lands? 



