344 ' ANNUAL EEPORT. 



in fact he recommends using two knives in the operation, one in 

 trimming off the diseased wood and the other in the lowest paring. 

 In a previous paper Professor Burrill has described the bacteria, 

 if memory is not at fault, as being so small that 250 of them could 

 stand in line across the edge of a sheet of writing paper. This 

 being true, it is suggested that a safer rule is to paint or wax all 

 wounds made in pruning, no matter how small. 



MR. PEFFER's views. 



Geo. P. Peffer, of Pewaukee, in the same number of the Review^ 

 has an article upon blight in fruit trees, in which some other ideas 

 are advanced, differing in part from those of Prof. Burrill. He 

 admits that blight may ensue from either of the following causes: 

 1st. Pressure of sap through the stomata of the young leaves and 

 new wood. 2d. Punctures 1^ insects. 3d. Rupturing the cdl structure 

 by freezing and thawing; electricity or electrical conditions of the 

 air; all these causing fermentation of the sap, inviting bacteria, 

 and, wnen decay sets in, fungi. He admits the theory of bacteria 

 to this extent, but finds another prevalent cause when no bacteria, 

 in his opinion, are present ; and that is in the early spring when 

 the evaporating surfaces of the trees are largely increased by the 

 opening blossoms and stimulated by high temperature. Then if 

 there are stoppages in the wood cells, occasioned by any kind of 

 injury to the structure of the newer wood or the last year's cam- 

 bium layer, the upward flow of sap is interrupted, and the leaves 

 and petals and all other surfaces of the blossoms dry up and wilt 

 for want of moisture from below to supply the waste by this exces- 

 sive evaporation. The leaf turns dark and finally black, the rotten 

 sap or poisonous fluid runs down the petal to the calyx, along the 

 little apple, then the stem of the little apple to the base, where all 

 the fruit stems started out of the flower- bud, and then all are 

 affected, if they had not been before. On most of the apple trees 

 it only runs down to the old wood and stops there, while on crab 

 or pear it is apt to run down the older wood, and so extend until 

 the tree is killed. Here Mr. Peffer thinks is a case where the bac- 

 teria or fungi are not the cause, though they may set in as soon as 

 fermentation and decay begin, and aggravate the disease. 



''A few years ago," says Mr. Peffer, "we experimented on apple 

 blossoms, and observed that the petals on the flowers wilted during 

 the day when the trees were about in full bloom, but before they 

 would naturally drop off. (We had at the time a southwest wind, 



