ADSORPTION AS A MEANS OF DETERMINING RELATIVE HARDINESS IN THE APPLE

Hardiness in the apple excites the greatest consideration when one is selecting varieties for an orchard in a northern latitude or in a region with a rigorous climate. The only definite procedure to ascertain this has been to grow the apple tree to bearing age. The underlying reasons why one variety of apple will maintain itself under climatic extremes of drought, heat and cold, while another will not, have been sought since pioneer days. The problem is of particular economic importance in the upper Mississippi valley because there are practically no commercial orchards of winter apples of any kind in this region. Orchardists, nursery men and fruit breeders, unmindful of the size of their task and the time factor involved, have attempted to secure by "trial and error" methods a knowledge of the nature of the conditions producing the qualities they sought. Considering the proposition from any point of view it would seem that a hardy variety must have some constant characteristic or combination of characteristics by which it may be distinguished from varieties which are tender, very early in life, and thus shorten the time and lessen the labor of selection in apple breeding. In considering a problem of this kind it should be borne in mind that the units of which plant tissue is composed are the cells and it is within these individual cells that the factor or combination of factors which make for hardiness reside. These cellular units may be regarded as colloidal systems, the greater part of which are hydrophilic in nature. It would only be natural to consider that in these colloidal materials are to be found the forces which make for hardiness.