PEACH YELLOWS AND LITTLE PEACH? 
MEL 1 COOK 
(WITH PLATES VI, V1) 
Peach yellows and little peach are well known but poorly under- 
stood diseases, and have been the subject of study by many workers 
for a number of years. Although they have engaged the efforts 
of some of our most efficient workers, the causes are as yet unknown, 
the symptoms not well defined from similar symptoms due to some 
other common causes, and the methods of control are very unsatis- 
factory. Although the researches have been directed along many 
lines, very little attention has been given to the morphology of the 
organs of the infected plants as compared with the morphology of 
corresponding organs on healthy trees. The fact that a knowledge 
of the morphology is frequently a very important factor for physio- 
logical studies has led to the preparation of this paper, hoping 
that the accumulation of data along various lines may eventually 
assist some student to solve this problem. 
The material used was taken from trees in an experimental 
orchard at Vineland, New Jersey, which was planted and managed 
by the Department of Horticulture of the New Jersey Agricultural 
Experimental Station. The trees were under constant observation, 
and there was no doubt as to their condition. The material was 
carefully collected during the early morning and mid-afternoon of 
a bright warm day in midsummer, when the conditions were 
exceptionally favorable for growth. Care was taken to select 
leaves of approximately the same age, and the same precaution 
was taken with the twigs. A great many sections were cut and a 
considerable number of drawings made, from which the figures 
shown in the plates were selected. 
The studies were based on a comparison of the structure of 
corresponding parts, the relative amounts of starch in these organs 
morning and afternoon, and its relative location. The studies of 
*Paper no. 29 of the Journal Series, New Jersey Agricultural Experiment 
Station, hoes of Plant Pathology. 
Botanical Gazette, vol. 72] [250 
