HISTORICAL NOTES. Aah 
HISTORICAL NOTES ON CROWN-GALL AND HAIRY-ROOT. 
The forms of the disease originally known as ‘‘crown-gall,” con- 
- sisting of fleshy outgrowths on the roots of fruit trees, have been 
known by nurserymen to occur in the United States for nearly half 
a century, although the first published mention of them is much later. 
In fact, about all the literature on the subject dates since 1890. No 
one can be certain as to the time of the first appearance of the disease 
in this country. In the opinion of the writer it was introduced with 
plants from Europe. The Europeans have known the disease, or a 
similar one, for many years. According to Sorauer (57 “) the Wurzel- 
kropf, which may be considered the same disease, occurs on the apple 
and the pear in Germany. 
Owing to its wide geographic distribution, crown-gall has attracted 
the attention of a number of investigators in this country. Bailey 
(5) and Stewart (62) in New York; Clinton (8) in Connecticut; Selby 
(49) in Ohio; Taft (65) in Michigan; Woodworth (79), Wickson (77), 
and W. E. Smith (56) in California; Toumey (68) in Arizona; Forbes 
(10) in Illinois; Alwood (1) and Phillips (40) in Virginia; and E. F. 
Smith (53), E. F. Smith and Townsend (54), von Schrenk (71), and 
Hedgcock (19) of this Department have published articles concerning 
the crown-gall forms of the disease. Others are cited later in this 
bulletin. 
The forms of the disease known as hairy-root have been observed 
by some of the older nurserymen ever since they have grown apple 
trees, dating back nearly fifty years. Attention was first called to 
the disease in this country by Stewart, Rolfs, and Hall (64). In 1900 
they described the simple form of hairy-root on apple seedlings in 
New York, giving it the name “‘hairy-root,’’ which had already been 
applied to the disease by nurserymen. This form and three other 
forms of the disease have since been recognized and described by the 
writer (21). 
In Europe at least two forms of the disease have been described 
by German investigators. That known in Germany as ‘“ Wurzel- 
krop{” is apparently identical with crown-gall. Frank (14) and 
Sorauer (58) have described this disease on the apple and the pear. 
A second form of the disease in Germany, which is apparently iden- 
tical with the aerial form of hairy-root, is called ‘‘Kropfmaser” by 
Frank (14) and Sorauer (61). Kissa (30) describes this disease on 
Pirus malus sinensis. Julie Jaeger (28) describes the same disease on 
the limbs of apple trees. Wakker (74) describes a similar disease on 
species of Ribes in Holland. 
@ The numbers in parentheses used in this paper refer to the index to literature on 
pp. 93-96. - 
186 
