Trunks of Apple Trees. 177 



and open by shrinking in warm and dry weather. Now, by this process, 

 heat or warmth will open these valves and evaporate the water in these globu- 

 lar cells and fit the sap for distribution, and the w^armer the air the faster the 

 work goes on and the faster the tree will grow, until an excess of heat or 

 cold deranges the working of this machinery. An over-supply by cold, 

 damp weather gives rust and mildew; an under-supply blight or sun-scald. 

 Now, the water-w'orks have to be repaired if out of order, and so have the 

 blighted trees to be attended to when it is first discovered. 



1. Eemove the affected parts as soon as possible by cutting o& the limbs 

 a little below the colored sap under the bark, or cut off where it is sound and 

 healthy. 



2. Mulch the ground under the tree or have a crop of clover or grass, or 

 any other crop that will shade the ground, thereby controlling sap circula- 

 tion. 



3. Plant trees when quite small, or better still, plant your seeds where you 

 want your trees to stand, so the main roots will go down deep into the sub- 

 soil, thereby retarding and eqiaalizing the new wood growth, so that a sudden 

 change of air will not stimulate overgrowth. This mode is particularly ad- 

 visable for planting the pear. 



Avoid stimulating manure and high cultivation unless the second and third 

 remarks are followed. 



The President — I presume this paper will be well considered after 

 hearing a paper by Prof. T. J. Burrill, of Illinois, on "The Trunks 

 of Apple Trees." 



Prof. Burrill, of Illinois — I too wish we had a blackboard here 

 this morning. I am so much of a school teacher I am almost lost 

 without one, whether I use it much or not. I think there is much 

 misapprehension about the sap passing through the cells in summer. 

 We all know the tree is made up 0f cells. In spring, before the 

 leaves put out, the cells are full of water, but in summer there is no 

 water in them. It soaks in the tissues of the tree, as water would 

 in the brick walls of a room. No sap goes between the bark and 

 wood. The bark separates easily because the cells are young there. 



TRUNKS OF APPLE TPtEES. 



BY PROF. T. .]. BURRILL, OF ILLINOIS. 



Throughout the Northwest orchardists have found, especially during the 

 last three years, the trunks of apple trees, in one 'way or another, seriously 

 injured or diseased. Sometimes the difficulty is limited to a small area, and 

 sometimes extends so as to ultimately kill the tree. Thousands of apple trees 

 have in this way perished in our own and adjoining States. It seems that no 



