222 TRANSACTIONS OF THE HORTICULTURAL 



For insttiiice. it would to many seem improbalile, if not impossible, 

 that a piece of green wood, Ijrouglit indoors from a temperature of 

 zero or below, should have in its tissues over forty per cent, of its 

 weight in water, and this not frozen, while at the same time a drop 

 of water ])ut upon its surface congeals instantly; l)ut this is true, 

 and can easily be verified by any one. What we call freezing is the 

 regular arrangement of the ultra-microscopical solid particles (mole- 

 cules) of which liquid water is composed. To become thus arranged 

 in definite order from the preceding condition of no order of associ- 

 tion, requires freedom of movement, and anything that impedes or 

 hinders such moveinent of these solid molecules hinders freezing. 

 When salt or sugar is put into water we say it is dissolved; that is, 

 the invisible solid molecules of the salt or sugar are disassociated 

 from each other and mixed through and through with the solid mole- 

 cules of the water, just as we might mix peas in sand. Now such a 

 mixture will not freeze at 32° Fahr. A saturated brine may be 

 cooled down to 4° Fahr. before ice forms, and then it is pure water 

 that becomes crystallized, not salt and water, though some of the 

 former may become mechanically entangled among the crystals. 

 Now, if a plant cell contains within its cavity pure liciuid water, this 

 will solidify at 32°, but if, instead of pure water, other substances 

 are dissolved in it, a lower temperature only will cause crystallization; 

 and the lower the stronger the solution. But healthy plants, in 

 proper winter condition, have no water in the liquid state in them. 

 The cells, not filled with other materials, have only air in their cavi- 

 ties. This is true even when forty per cent, by weight can be arti- 

 ficially evaporated from green wood. The water is mostly in the 

 texture of the cell ladls, in a state of molecular mixture with the 

 molecules of the plant substance, and the whole is a true solid. 

 Freezing cannot take place until the crystallizing power is strong 

 enough to force these water molecules out from among the others, 

 and the force required depends upon the attractive power between 

 such molecular particles. Grains of wheat holding in this way about 

 one-tenth part of their weight in water (not as a liquid), have re- 

 sisted — 70° Fahr. without injury, and without the contained water 

 freezing. 



But by far greater destruction has come to our orchard trees 

 through another form of injury by frost. A longitudinal crack, 

 aside from the exposed wound, does no particular harm to the tree. 

 If afterwards protected from the effects of weather and enemies, even 

 the cells along split surfaces may retain full vitality, and the whole 

 tree grow as well afterwards as before. Not so, very often, in 

 that to be now described. Many thousands of promising apple 

 trees have been killed outright, or so injured as to be worthless, 

 in our part of the country during the last few winters, by the bark 

 separating from the wood a part or the whole of the way around the 

 •trunk, usually near the ground. Because the trees do not, perhaps, 



