STATE HORTICULTUKAL SOCIETY. 343 



the meantime the bacteria increase prodigiously in number and 

 gradually spread to the surrounding cells, passing through the, 

 structure by means of their own, rather than carried by the move- 

 ments of the sap. Progress is always slow, rarely more, under the 

 most favorable conditions, than half an inch per day (twenty-four 

 hours), in young growth — much slower in older bark. In the 

 trunk of one apple tree, carefully watched after an inoculation, in 

 June, the organisms remained in an active state eleven months 

 and only spread during the time four inches. 



After noting the fact that certain varieties are less subject to 

 blight than others and that certain soils and exposures are more 

 favorable than others to resist it, he recommends remedial efforts 

 to exclude the bacteria from the trees : "It must be under- 

 stood that the disease always starts in some part of the top of the 

 tree, never in the roots; and the disease agents come from without^ 

 never from the inner tissues. On the^ stigma (end of pistil or 

 young pod) of the flower they enter the cells without the necessity 

 of a wound, for there is no protective covering here like the epi- 

 dermis or bark. Whenever, however, the living cells are covered 

 by a coating of corky tissue, like the dead outer bark, or by an un- 

 broken epidermis or skin, the bacteria can not gain entrance 

 without mechanical help in the way of a crack, a puncture, or 

 other wound. Though the disease is readily transferable by 

 inoculation, no results ordinarily follow tying a badly blighted 

 limb among the branches of a healthy tree." 



Hence if his meaning is understood correctly, if there is no rupture 

 of the bark by a diseased condition of growth, or by outside injury^ 

 no openings made in the cell structure, the bacteria cannot enter 

 except through the blossoms as above stated. The first remedy^ 

 therefore, as recommended by Professor Burrill, is to maintain a 

 healthy, constant, but moderate growth of the tree, especially in 

 the early part of the season, that the wood may become well 

 ripened and less liable to rupture from climatic causes. 2d. To 

 prune early in the spring, before the buds start, if any pruning is 

 necessary, and all wounds more than three-fourths of an inch ia 

 diameter to be covered with linseed oil and lead paint. 3d. Ta 

 wash with a strong alkaline solution at least once a year to keep 

 the bark smooth and clean, results useful in themselves, but espe- 

 cially useful in aiding us to detect blight in its first infection, 4th. 

 To carefully remove all affected parts as soon as discovered, cutting 

 far enough away from the discolored parts to make sure against 

 inoculating healthy tissue by carrying the bacteria on the knife; 



