LETTER OE TRANSMFITAL. 



U. S. Department of AaRicuLTURE, 

 Division of Vegetable Pathology, 



Washington, D, C, December 7, 1893, 

 Sin: I have tlie lionor to transmit lierewitli a report oii experiments 

 made during tlie past two years in the pollination of pear flowers. 

 This Avork, which has been carried on under my direction by Mr. 

 M. B. Waite, was tlie outgrowth of some investigations of fire or twig 

 blight of the pear. In the study of this disease and the life liis- 

 tory of the microorganism causing it, an attempt was made to obtain 

 some information in regard to the relation of insects to the malady in 

 question. It was found that the blight bacteria were carried from 

 flower to flower by insects, the disease being rapidly disseminated in 

 tliis way. The question then arose as to the possibility of preventing 

 blossom blight by excluding insects, and of course along with this it 

 became necessary to consider the effect on fruitfulnes.s of stopping all 

 insect visits. The preliminary experiments along these lines gave 

 results which were somewhat startling, as they seemed to clearlj^ indi- 

 cate a fact hitherto not recognized by scientific- and practical horticul- 

 turists, viz, that many of our well-known varieties of peafs are wholly 

 unable to fertilize themselves. In other words, Avhenever insects are 

 excluded and cross-fertilization prevented mostof the common varieties 

 of pears, although they may blossom profusely, fail to set fruit. To 

 obtain further facts on this important matter extensive experiments 

 were made during the spring of 1892 in Virginia and New York, the 

 results in each case fully confirming those of the previous year. From 

 a practical standpoint the work is of .great importance, as it enables us 

 to throw light on many questions connected with the unfruitfulness of 

 orchards not hitherto understood. These points, together with full 

 details of the exj^eriments, are discussed in the accompanying report. 

 Eespectfully, 



B. T. Galloway, 



Ch ief of Divis ion 



Hon. J. Steiiling Morton, 



Secretary of Agriculture^ 



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