
          94

"It is very doubtful as to the roots being in any special sense
the chief <s>sort</s> seat of the disease.  In my specimens the roots were not
infected at all, neither can we suppose the organisms believed to
be the exciting cause lives in the earth.  The contagion is rather 
in the tops from which the roots as well may be infected." pp.
134-5.

Prof. Burrill say, Ibid. p. 135, that Lombardy poplars are such
subject to pear blight and that the disease can be communicated
from one to the other.  Cf. previous statement of supposed relations
of this tree to yellows. Page - 23.

"In Science for Sept. 23, 1880, p. 162, there appeared an abstract
of a paper read by me before the Am. Soc. of Microscopists
at Detroit upon the blight of pear and apple trees.  In this paper
I expressed the opinion that the yellows of the peach tree
would be found due to an organism similar to that found to be the 
cause of pear tree blight.  This opinion was based on my
knowledge of the latter disease, upon the thoroughly confirmed
contagious character of the yellows, upon the failure of competent
investigators [Halsted, etc. probably] to find, after extended research,
anything like the ordinary parasitic fungi.  It was long
ago conceded by entomologists that the disease did not arise from
the depredations of insects.
        