232 
able that the contagion does not enter the tree through ordinary wounds 
caused by men or animals. 
(4) The fact that the disease can be transmitted artificially through 
the root system makes it probable that trees may also become infected 
naturally in this way. 
(5) Experimental proof of the identity of the peach rosette and the 
plum rosette is still incomplete. 
(G) None of the yeasts or bacteria found in the cultures made from 
diseased tissues produced the disease when inserted into the cambium, 
and it is probable that the disease is not due to such organisms. 
(7) In both natural cases and those induced by budding, the disease 
progresses gradually from the point of infection until all parts of the 
tree are involved. Even when a tree shows symptoms in all parts at 
once, as is very often the case in early spring, we may assume that 
the cause of infection entered through the roots during the previous 
summer or autumn and was gradually diffused through the whole tree 
in the months immediately preceding the vernal symptoms, as was cer¬ 
tainly the case in the seven root-grafted trees. 
(8) The shortest period of incubation was about two months (Bull. 
No. 1, p. 49) and the longest period about ten months, but one-half of 
this longest period was the winter season, during which the trees were 
dormant. 
(9) The disease is probably conveyed through the protoplasm and the 
failure to isolate any pathogenic yeast or bacterium suggests the pos¬ 
sibility that the cause is some amoeboid organism living in the pro¬ 
toplasm and so much resembling it as to be difficult of detection. 
Such an hypothesis would explain all the facts. That the disease is 
due to any chemical ferment or other readily soluble substance seems 
out of the question, for the upward and side movements of the water 
imbibed by the roots would certainly carry it to all parts of the grow¬ 
ing tree within a few hours or a few days at longest. Moreover, such 
a substance possesses no indefinite power of multiplication. Whereas, 
in this disease a very small fragment will induce symptoms in a whole 
tree, any part of which will then induce the disease in another tree. 
REMEDIES FOR THE ALMOND DISEASE CAUSED BY CERCOSPORA 
CIRCUMSCISSA, SACC. 
By Newton B. Pierce. 
[Plates xvm-xx.] 
Since the publication of the author’s former paper on the almond 
disease so prevalent in southern California,* spraying experiments 
have been conducted in Orange County, which have clearly demon- 
* Journal of Mycology, Yol. vn. No. 2, pp. GG-77. 
