Trunks of Apple Tree& 



183 



such can be found in the cell-cavities or other openings of the living tissues ; 

 yet by heat under 212° Fahr., forty per cent, by weight of water can be driven 

 off. It is molecularly distributed among the elementary bodies of cellulose, 

 protoplasm, starch, etc., all of which are much too minute to be seen with our 

 best microscopes, but which as certainly exist as do worlds beyond the reach 

 of telescopes, and both are as certain as human knowledge at its best. 



I append a table of the proportions of water determined by evaporation in 

 an oven kept below 212° Fahr., in the trunks of several trees cut in Decem- 

 ber, 1883. Where two numbers are given in a column the first shows the 

 Avater in the inner portion, and the second in the succeeding ring of growth : 



Trees. 



Diam. 

 In. 



Per cent, of Water 

 Sap. 



Hewes' Virginia Crab, No. 1 4 



Hewes' Virginia Crab, No. 2 4 



Wilson's Sweet 6 



Box Elder 4 



Box Elder 5 



Box Elder 3 



Soft Maple 4 



In the spring some of these trees would contain a greater per cent, of 

 water, but I have no figures for the amount. What has now been given may 

 be a surprise to many, and the query would hardly be unnatural, " Why do 

 not all the tree trunks burst when exposed to a freezing temperature ? " If, 

 however, the internal wood is sound — rotten wood soaks up great quantities 

 of water — and the spring activities of the roots have not commenced, it is 

 not likely that the trunks of any trees will bvirst by the swelling of ice for- 

 mation ; whether or not the shrinking of the tissues by cold without concur- 

 rent freezing is with us ever sufficient to cause the longitudinal cracks we 

 observe after the manner of shrinking by drying, I can not tell. Probably 

 the bark may sometiines part through this cause. The tendency to such 

 cracking by the change in size as the temperature decreases is just as certain 

 as by the change through drying by heat. The only question is as to the 

 amount of contraction by such cold as w'e have. Probably no trees ever burst 

 until the thermometer marks zero or below, and then only when the heart is 

 more or less rotten, or after the roots have started to absorb quantities of 

 water from the soil, as in springtime. 



But this cracking open of the bark, or the latter and the wood, does com- 

 paratively little injury. It simply makes a bad wound without in the least 



