EXUDATIONS AND ROTTING. 239 



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. Bakf., 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, 

 Bjill. 94 of Cornell University Agric. Expt. Statiort, 1895, 

 P- 233. 



On Bacteriosis in Turnips, see Potter, Proc. R. S. 1901, Vol. 

 LXVIL, p. 442. 



