224 TRANSACTIONS OF THE HORTICULTURAL 



of germination, about ten per cent, by weight of water, and in the 

 trunks of trees in good winter condition forty per cent, of water. 

 The intimate intermixture of the particles of water with the others 

 spoken of comes al)out through the life processes of the plant, and 

 cannot be so blended by mechanical means. A dead and dry piece of 

 wood will quickly absorb water, Init the latter does not so completely 

 lose its liquid character, and crystallizes at or near 32° when exposed 

 to cold. 



If now we inquire what conditions of the tree render it liable 

 to crack open by frost, w^e should say, 1st, The engorgement of water 

 by the action of the roots in a comparatively warm soil. By this 

 means the ducts, cell cavities and intercellular spaces, are all filled 

 with liquid water, as we know is the case with maple trees in spring 

 time. In such condition severe freezing can hardly help but result 

 in the splitting of the trunk. 2d, Unsound heartwood which absorbs 

 an undue amount of water from the wet soil; and 3d. Soft unripe 

 outer layers, which by shrinking as described above from two causes, 

 burst. In the case of the separation of the bark, we must look for 

 the most part to the condition of the last 3'ear's growth, not very 

 much to the interior tissues. When the summer has been favorable, 

 the cultivation wisely done, the tree in good vigor and the young 

 growth well ripened, very severe cold will be withstood without in- 

 jury; but with the opposite set of conditions when freezing occurs, 

 rupture results. Something depends upon the peculiarities of the 

 variety, in the case of apple trees; something on the management of 

 cultivators in several ways; but, after considerable observation, it 

 seems to me that a summer drouth followed by a warm and moist 

 autumn, and then by severe freezing, is the combination of causes 

 most damaging. If the growth and other physiological processes are 

 checked in midsummer, the tree may be poorly prepared for the vicis- 

 situdes of winter, without further enfeeblement; but when, through 

 the starting of new growth in autumn the last formed cells are left 

 without the possibility of maturing, injury is much more liable to 

 follow. When plants have normally completed their season's growth, 

 such autumn stimulation does not affect them with anything of the 

 likelihood in the former case. The more severe the summer's 

 check, the more readily the growth in autumn starts, and the less 

 ready the tree for winter. The only apparent reason for the injury 

 under consideration occurring near the ground rather than else- 

 where, is the fact that in autumn the ground is warmer than the air 

 and thus more and later growth may take place at the base of the 

 trunk. 



My attention was specially called by Mr. B. F. Johnson, of 

 Champaign, during the last summer and autumn to the healthf ulness 

 of orchards on flat lands, while those upon the higher ridges — the 

 sites usually supposed best — were badly diseased. Several trips were 

 made by us together to study the facts and if possible their explana- 



