MICROSCOPIC INVESTIGATION. 191 



There may be periodic times when fruit-trees and cereals will attain 

 great perfection in growth, and appear wholly free fronj, external fungoid 

 disease, notwithstanding the soil, either mechanically or chemically con- 

 sidered, is not of the most favorable character. Such appearances may 

 lead to an extension of fruit-tree planting on such soil ; but with a 

 single nnlavorable season the fruit-grower's hopes may perish with his 

 trees and labors. Torulacei fungi seem ever present, waiting in unde- 

 veloped forms their time for action. 



My present experience leadsme to suppose that j)ear-tree blight is a 

 local fungus fermentation of the genus Torula, and which may be de- 

 veloped under any one of a number of causes. Every condition that 

 will prevent the bark and shoots from ripening will foster under high 

 temperatures, in the presence of organic acid, (which is always present 

 in green or unripe wood,) and vegetable nitrogeueous matter, one or 

 more species of Torulacei fungi. Stagnant water in the ground contain- 

 ing the drainings of decomposing organic matter is always charged with 

 Torulacei budding spores and germinal matter, which if absorbed by the 

 roots will certainly contaminate the sap of the tree. When small 

 branches are attacked it may i^rove best to remove them, but the main 

 branches and trunk may be saved by prompt action. The stained bark 

 should be removed as soou as observed, and before the stain has gir- 

 dled the branch or trunk, as may be. If not removed the sap-wood 

 will be poisoned. In the case of atmosphere blight, that is when the 

 fermentation is produced from the immediate action of high tempera- 

 tures on the outer bark, favored by previous conditions, the fermentation 

 will proceed from the surface to the interior,- but in the case of root ab- 

 sorption the fermentation will proceed from the sap-wood to the exterior. 

 The removal of the tree to a more favorable place, or drainage, will 

 probably save the affected tree in the case of root absorption. 



Barry, on fruit-gardening, says, page 361, that '•' Blight has never 

 been known to originate on the dry, sandy loam of Long Island, not 

 even with heavy manuriug, the drought of midsummer always ripeniug 

 the shoots so completely that the leaves drop off long before frost com- 

 mences." 



Some interesting experijnents have been prosecuted by Mr. William 

 Saunders, superintendent of the Department grounds, in relation to 

 pear-tree blight, particularly during the last two years. A pear-tree 

 which was badly blighted on its main trunk was made the subject of 

 special experiment. Nearly all of the bark was blighted within three 

 feet of the ground, only about an inch and a half in width being left to 

 connect the upper part of the tree with the unblighted bark at the base. 

 The aifected part was removed and the sap-wood left quite exposed to 

 view ; but to prevent injury from the air it was at once coated with a 

 composition of carbolic acid, sulphur, lime, and water, and used as a 

 liaint. After the lapse of two years the tree has wholly recovered, 

 and the denuded part is again covered with new undhealthy bark. The 

 tree in all respects presents a healthy appearance. Many other trees 

 much affected with blight were coated heavily with the sulphur com- 

 positions, and have evinced marked signs of improvement. It is intended 

 to continue these experiments on a larger scale, until sufficiently numer- 

 ous and well-established facts attest the best mode of treatment. The 

 Department grounds consist of a heavy, compact, partially undrained 

 soil, lying low ; they are therefore unfavorable for the highest develop- 

 ment of liear-tree culture. It has been only by persistent effort that the 

 fruit-trees on the Department grounds have been brought to their 

 present highly improved state. 



