Bark Canker Disease of Apple Trees. Grace G. Gilchrist. 243 
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Fig. 
REFERENCES. 
EpGERToN, C. W,—Two little known Myxosporiums. Ann, Mycol. v1, 
p. 48 (1908). : 
Lewis, C. E.—Inoculation Experiments with fungi associated with apple 
leaf spot and canker. Phytopathology, II, p. 49 (1912). 
STEWART, F. C., Roirs, F. M. and Hatt, F. H.—A Fruit Disease Survey 
of Western New York in 1900. New York Agric. Expt. Sta. Bull., 
No. 191, p. 298 (1900). 
HEsvter, L. R. and WuHeEtTzEL, H. H.—Manual of Fruit Diseases. New 
York, pp. 130-132 (1917). 
PETHYBRIDGE, G. H.—Notes on some saprophytic species of fungi, asso- 
ciated with diseased potato plants and tubers. Trans. Brit. Mycol. 
Soc. VI, p. 104 (1919). 
MarcHalL, Ev. et Em.—Contribution a l’étude des champignons fructi- 
coles de Belgique. Bull. Soc. Roy. Bot. Belg. Liv, p. 109 (1921). 
DESCRIPTION OF PLATES. 
PLATE IX. 
. 1. Typical scar caused by Myxosporium corticolum Edgert. on apple tree, 
5 November, 1920. 
. 2. Whole branch of James Grieve apple tree killed by M. corticolum, 
24 August, 1921. 
. 3. Near view of same branch. 
. 4. Near view of same branch showing new scar forming. 
. 5. Scar caused by M. corticolum completely healed over by the growth 
of wound wood. 
. 5a. Scar of M. corticolum with dead spurs. 
. 6. Pustules of M. corticolum on James Grieve, 29 October, 1920. 
. 7. M. corticolum on young standard apple tree, Sandford, Somerset, 
December, 1921. 
8. (a) Tr. section of apple branch showing line of dead tissue in phloem (a). 
(6) Portion of above. x10. ¥=xylem; p=phloem; m=medullary ray; 
d =dead tissue; f =fibres. 
(c) Same. x45. c=crystals of calcium oxalate. 
PLATE X. 
g. Streak culture of M. corticolum showing formation of spore masses on 
malt extract agar, January, 1922. 
to. Tr.sections (4 cm. thick) of branch shown in Figs. 2, 3, 4,25 August, 1921. 
11. Plate culture of M. corticolum on prune extract agar, incubated at 
20° C., four weeks old, 11 March, 1922. 
Fig. 12. Germination of single spore of M. corticolum. 
(a) November 15, 11.30a.m. x 100. (e) November 18, 9.45 a.m. x 100. 
(b) a TOs 3°45)p mle a TOOL (Op) 4 I9, II.I5 a.m. xX I0o. 
(c) _ 07, Di.DSia.ms Xx Too! . (2g) 5 20, 10 a.m. x 100. 
(d) - I7s) 5ol5ip-m. reo, | (72) ee 22, 00.30 a.m. x0: 
PLaTeE XI. 
Fig. 13. Mycelium of M. corticolum in the wood of apple. h.p.=hypha 
entering pit; h=hypha; p=pit; m=medullary ray. x 180. 
Fig. 14. Long. section of wood vessel showing hypha passing into pit. x 420. 
Fig. 15. Long. section of wood vessel. x 420. 
Fig. 16. Spores of M. corticolum from James Grieve apple tree. x 260. 
Fig. 17. (a) Tr. section of apple bark. Ist stage of acervulus. h=hypha. x 130. 
(b) fs 4s 2nd stage. y=stretched radial walls of 
bark. x130. 
(c) Ay 5 3rd stage. x I00. 
(a) - _ 4th stage. c=conidium. x90. 
(e) 5th stage. x 100. 
(f) Development of a conidium. x 390. 
16—2 
