478 
J. G. GROSSENBACHER 
mittently during many years; in the early days of phytopathology 
considerable attention was given to these diseases and much valuable 
information was accumulated. The subsequent enormous develop- 
ment of mycology, in its relation to the diseases of plants in general, 
has eclipsed and supplanted the interest formerly centered on bark 
diseases, apparently because the mycological phases afforded more 
tangible subjects for investigation. Most of the more modern at- 
tempts at the study of crown-rot have been of a preliminary nature 
and have led only to hazy or ill-founded conclusions. 
Some of the apparently new ideas that occurred to me during 
the earlier part of this investigation were published in 1909,^ while 
others were stored away, embodied in the form of notes and photo- 
graphs to be used later. Continued search of the older literature of 
botany and forestry for observations upon bark diseases, as well as 
with reference to the question of radial growth ,2 resulted in gradually 
placing one after another of my supposed new ideas in the category 
of confirmatory observations and conclusions. 
The Literature.- — The literature accumulated on crown-rot and 
related subjects during the past six years has become very voluminous, 
and to attempt a review seems rather discouraging. Most of the 
important papers on radial growth, and on certain of the factors 
determining its distribution, were reviewed some time ago in the 
last cited paper. Many of the more general papers on this disease 
and some of those dealing with the cause of the trouble were discussed 
in my two former papers on crown-rot. There are still too many 
abstracts of such papers on hand to be fully utilized in this connection, 
and therefore only a few of the most pertinent ones will be mentioned 
later in the discussion of my results. 
The Causes of Crown-Rot. — The common orchard bark-fungi are 
evidently the causes of the rotting of the bark in crown-rotted trees, 
but the cause of the initial injuries that led to the death of this bark 
has not been experimentally determined, although some work upon 
this problem has been done on citrus trees in Florida. Field observa- 
tions in the north, together with a few experiments, have shown that 
the manner and timeliness of radial growth, pruning, and the occur- 
1 Crown-rot, Arsenical Poisoning and Winter Injury, N. Y. Agr. Exp. Sta. 
Tech. Bull. 12: 369. 1909, 
2 The Periodicity and Distribution of Radial Growth in Trees and Their Rela- 
tion to the Development of "Annual" Rings, Trans. Wise. Acad. Sci. Arts and Letters 
18: I. 1915. 
