252 Report of the Botanical Department of the 



varieties are most subject to the disease. It appeared that certain 

 surroundings and locations are typical of crown-rotted trees, and 

 other things being equal, that the different varieties seemed to possess 

 a rather definite relative liability to the disease. An environment or 

 season which induces the origin or production of tissues that for one 

 reason or another could not be fully matured or differentiated before 

 the close of the vegetative season, seemed to be associated with the 

 occurrence of crown-rot. Whether the completion of growth or full 

 maturation of the tissues is prevented by low temperature or some 

 other untoward conditions such as drought, etc., the net result may 

 be the same. A tree is thus forced into a dormant period of severe 

 environment in an abnormal and susceptible state. The main varietal 

 characteristics that were noticed as distinguishing the more sus- 

 ceptible from other varieties are the habits of rapid growth and early 

 bearing. 



Another environmental factor, which in general is noticeably related 

 to the occurrence of crown-rot, is the wind. The relative wind ex- 

 posure was frequently the only observable difference in the environ- 

 ment of neighboring orchards, one of which was severely affected, 

 the other but Uttle if at all. The direction of the prevailing 

 wind of a locality or its direction during a critical period usually 

 corresponds to the side of maximal injury. 



The economic relations of crown-rot are of more consequence than 

 appears at first sight, because the lives of affected trees are involved. 

 In case of diseases of foliage or fruit the damages are largely confined 

 to one season while from this type of disease a loss may be sustained 

 which amounts to several years of time and a considerable outlay 

 of money. 



FIELD OBSERVATIONS. 



introductory. 



During late summer of 1909 a short study was made of a few crown- 

 rotted orchards. The most severely affected trees were easily dis- 

 cerned at a distance by their rather sparse and prematurely yellowing 

 foliage. On examination at close range it was found that such trees 

 had large areas of dead, decaying bark somewhere on the stem, usually 

 at the crown or about the bases of the upper roots. In fact in many 

 such cases the decaying bark completely girdled the crown and in 

 others the bark of all the lateral roots, as well as of the stump, was 

 entirely dead and decayed, thus leaving only a few small roots under 

 the center of the tree intact and available for the absorption of soil 

 solutions. By making numerous cross and longitudinal sections it 

 was found that in many instances both the alburnum and duramen 

 were discolored or even decayed. In these same orchards, however, 

 were apparently normal trees having injuries of the same type sur- 



