130 Buthkr—A Study on Gummosis of Prunus and Citrus, with 
one may gather from the fact that the outflow of the gum does not corre- 
spond to places of injury, as it always does when the latter are the inciting 
cause. The autogenous development of gummosis is, however, much less 
common than that resulting from direct injuries to the cambium. 
At one time it was believed that gummosis was due to one or, at most, 
several forms of injury, but to-day it must be admitted that, provided the 
plant is in the proper condition when wounded, any traumatism will pro- 
duce the malady. This will be clearly shown in the following examples. 
1. Gummosis is produced by a variety of parasitic Fungi, to wit:— 
Coryneum Beyerinckii, which is capable of producing marked gummosis in 
the peach ;! Clasterosporium carpophilum, Lev. Aderh.’, a common parasite 
of the cherry, plum, peach, and almond; Sclerotinia fructigena, (Pers.) 
Shroet.; Cladosporium ecpiphyllum;* Valsa leucostoma, Pers.; Tubercu- 
laria vulgaris, Tode; Botrytis cinerea, Pers.;* Plowrightia morbosa, (Schw.) 
Sace.; Exoascus deformans, (Berk.) Fuckel.° 
2. According to the researches of Aderhold and Ruhland ® on the one 
hand, and of Brzezinski? on the other, it would appear that Bacteria also 
produce gummosis; the former have described a species of Bacillus that 
induces the malady in the cherry, and the latter has isolated a Bacterium 
from the peach, plum, and apricot which he believes is the cause of the 
disease in these trees. 
3. Certain insects or their larvae also cause more or less copious 
gumming: the peach-borer, the curculio on the fruit of plums, the 
larvae of Tortrix woeberiana, Shiff§ Gummosis may also be produced by 
piercing the young shoots near the apex with a needle,® tearing the bark, 
knife-wounds, bruising the bark with a mallet. This latter method I have 
tried experimentally on orchard trees, but not with very marked success. 
I hammered the bark of peach, cherry, and plum limbs, being careful not to 
cause rifts. Gum appeared on the surface in 10 % of the wounded cherries 
and in 50 % of the wounded peaches and plums. 
4. Gummosis may be produced in young shoots by burning with a hot 
iron, and freezing ; chemical agents are, however, very much more effective. 
I have successfully used sulphuric (Pl. VIII, upper left-hand figure), phos- 
phoric, nitric, and lactic acids ; acetic acid, on the other hand, has given me 
* Smith, R. E.: Peach Blight. California Agr. Expt. Sta. Bull. 
2 Aderhold, R.: Uber Clasterosporium carpophilum, 8c., loc. cit., ante. 
$ Massee, G.: A Textbook of Plant Diseases, p. 306. 
4 Rant, A.: De Gummosis der Amygdalaceae. 
* Pierce, N, B. : Peach-leaf Curl: its Nature and Treatment. U.S. Dept. Agr., Div. Veg. Path. 
and Phys., Bull. xx. 
® Aderhold, R., and Rubland, W. ; Der Bakterienbrand der Kirschbaume. Arbeiten kaiserl. 
biolog. Anstalt, v, 1907, pp. 293-340. 
7 Brzezinski, P. J.: Etiologie du chancre et de la gomme des arbres fruitiers. Comptes Rendus, 
exxxiv, 1902, pp. 1170-3. . 
Rant, A.; loc. cit, ® Beijerinck, M. W., and Rant, A.; los, cit, ante, 
