376 



THE GARDENER'S MONTHLY 



rience of many matters referred to, that they are j to work up these advantages are better it strikes 



just as stated here. There is no doubt that 

 Louisiana has the material for building up one 

 of the greatest States in this Union. The efforts 

 making by Col. Dennett to get people to see and 



us, than millions of political speeches, and we. 

 wish them every success. The book is sent free 

 by mail by Col. Dennett, New Orleans, for 60 

 cents. 



MORTICULTURAL rSoCIETIES. 



COMMUNIGA TIONS. 



POTOMAC FRUIT GROWERS. 



BY G. F. XEEDHAM. 



Prof. Brainard, Chairman of the Scientific 

 Committee, read a paper on Pear Blight. 



After an elaborate discussion of plant growth, 

 he said : " The green and tender portions of 

 the tree are made up of cello, whose membranous 

 walls are very thin and delicate ; consequently, 

 when the sap, with which these walls are always 

 filled, is subject to sudden expansion, from either 

 high or low temperature, the cell walls are rup- 

 tured and the sap runs out. A putrefaction con- 

 dition soon follows, giving rise to fungoid growth, 

 if other conditions are favorable. 



" There are two causes that produce the rup- 

 ture of these newly formed cells, and their action 

 is very sudden and certain. These are extremes 

 of heat and cold. 



" In the spring of 1875, in Ohio and along the 

 lake shore fruit region, after the trees had put 

 forth their leaves, a sudden fall of temperature 

 from summer heat to from 12° to 15° below freez- 

 ing killed outright nearly every pear tree in that 

 extensive fruit district. I examined many of 

 these trees soon after, and found the external 

 appearance exactly similar to what is called 

 fire-blight. 



" In order to test the influence of heat in pro- 

 ducing the blight, I have subjected a vigorous 

 and healthy.branch of a pear tree to an artificial 

 heat of 108° Far., for 20 minutes. The effect upon 

 the leaves and soft wood was vastly like the 

 natural blight. 



"The normal heat for the fruit-producing sea- 

 son ranges from 65° to 85°, the mean of which 

 is 70°. A temperature of 95° is dangerous, and 

 100° and higher is disastrous. 



"From careful ob-servation and inquiry, I have 

 found the trees upon a southern exposure much 



more liable to blight than those on a 

 northern or north-eastern exposure." 



The Prof, then gave several examples to sus- 

 tain his position. "A gentleman has a pear 

 orchard near the city, which has a northern 

 exposure. This orchard has not been affected by 

 the blight, while trees in the vicinity with a 

 southern exposure have been completely de- 

 stroyed. Another had pear trees on a southern 

 exposure which were troubled with the blight. 

 These he removed to a northern exposure, and 

 they soon became healthy and fruitful, and no 

 blight has since aflfected them. <fec. &c. 



" Keep your trees low-headed, and plant with a 

 northern exposure, and you will take the most 

 important measures to prevent the pear blight." 



[We always give our correspondents free 

 scope, and of course are not responsible for their 

 opinions. The effort of Prof. Brainard to ascer- 

 tain the cause of pear blight by experiment, will 

 attract attention at once, as the majority of those 

 who profess to understand the disease will write 

 for a year in preference to observing for an hour. 

 In regard to the experiment itself, the fire-blight 

 does not commence in the "leaves and soft wood," 

 so that the analogy goes for nothing. Fire-blight 

 commences in spots on the bark, often extending 

 round the whole stem and girdling it— and not 

 unless it does extend round and girdle the 

 branch is there any injurious effect on " leaves 

 and soft wood." The line between the healthy 

 and unhealthy part is often so distinct as to be 

 drawn by a hair line, and it is inconceivable that 

 say one inch of bark should be injured by 108°, 

 and an inch adjoining, separated but by a line, 

 should be under the same temperature, and 

 yet absolutely uninjured. The whole courae of 

 the Professor's argument, as well as of many 

 other recent writers on fire-blight on the apple 

 and pear, shows that he is thinking of some 

 other disease than fire-blight, or else has given 

 the appearances in the real disease, but a very 

 cursory examination. — Ed. G. M.j 



