Notes to Chapter XXV.
The rotting of bulbs, roots, etc., has been much discussed during the last few years in the pages of the Gardeners' Chronicle, Zeitschrift für Pflanzenkh., and elsewhere. The principal references to Bacteriosis—the rot in which bacteria are stated to be the primary agent causing these and similar diseases—may be found in Massee, Diseases of Plants, pp. 338-342, and more fully in Russell, Bacteria in their Relation to Vegetable Tissue, Baltimore, 1892; and in Migula, Kritische Uebersicht derjenigen Pflanzen-krankheiten, welche Angeblich durch Bakterien verursacht werden, Semarang, 1892.
The most convincing accounts, however, are since that date; see Smith, "Pseudomonas Campestris," Cent. f. Bakt., B. III., 1897, p. 284, and Arthur and Bolley, Bacteriosis of Carnations, Perdue University Agr. Expt. Station, 1896, Vol. VII., p. 17. Woods has lately shown that this disease is due to Aphides only, the bacteria having nothing to do with the disease primarily, Stigmonose, Bull. 19, U.S. Dept. Agr., 1900; but it is necessary to bear in mind that actual penetration of the cell-walls from without must be proved, as De Bary proved it for germ-tubes of fungi, before the evidence that Bacteria are truly parasitic in living plants can be called decisive. This is a difficult matter, but until it is settled we do not know whether these organisms are really parasitic in the sense that Phytophthora is, or merely gain access by other means—I have traced them through dead fungus-hyphae—to the vessels, dead cell-walls, etc. The proof of infection via water pores and vessels is given for one species by Harding, "Die Schwarze Faulnis der Kohls," etc., Cent. f. Bakt., Abh. II., B. VI., 1900, p. 305, with literature.
Concerning the "Damping off" of seedlings, see Marshall Ward, "Observations on the Genus Pythium," Quart. Journ. Microsc. Soc., Vol. XXIII., 1883, p. 485, and Atkinson, Bull. 94 of Cornell University Agric. Expt. Station, 1895, p. 233.
On Bacteriosis in Turnips, see Potter, Proc. R. S. 1901, Vol. LXVII., p. 442.
CHAPTER XXVI.
NECROTIC DISEASES.
Patches—Frost-patches—Bruising due to hail, shot, etc.—Fire—Sun-burn or scorching—Sun-cracks. Dying-back—Frost—Fungi—Wound fungi—Defoliation by insects—Defoliation by hand—Staghead.