642 The American Naturalist. [August, 
Fernbach” Vestea, Kramer,” and Russell.” Even when 
purposely introduced into living tissues they refuse to grow or 
spread but little and finally die out,” unless they possess 
specific pathogenic power in which case the result is quite 
different. 
The diseases which will be discussed in the following pages 
may be divided into four classes: 
(1). Diseases of clearly established bacterial origin. 
(2). Diseases which appear to be constantly associated with 
bacteria and which are probably due to some specific organism, 
but full proof of which has not been furnished. 
(3). Diseases said to be more or less closely associated with 
the presence of bacteria and ascribed thereto, but in which 
little or no proof has been brought forward to establish the 
causal relation. 
_ (A). Communicable diseases which have been ascribed to 
bacteria but associated with which no organism has been found 
and which are probably of non-bacterial nature. 
On the whole it would perhaps be more logical to divide the 
following pages into four chapters in the way I have specified, 
but for practical reasons it has seemed better to discuss all of 
the diseases of a given plant in one place. I have, therefore, 
arranged the material by hosts, but will at the close try to 
summarize the whole subject in the manner above indicated. 
It will certainly be some time, probably many years, before 
we have anything like a permanent scheme of classification for 
the bacteria. Our knowledge is still too incomplete. Meanwhile, 
we have to do the best we can with the present systems, all of 
11(17) De Vabsence ere microbes dans les tissus vegetaux. Annales de l’ Inst. 
Pasteur, 1888, pp. 567-5 
" (18) De l'absence an microbes dans les tissus. /ééd., 1888, p. 670-671. 
19 (19) Bakteriologische Untersuchungen ueber die Nassfäule der Kartoffel- 
knollen. Osterreichisches landw. Centralb, I, Heft 1, 1891. 
Plc 
be Louies: (2@) On the parasitism when introduced into plants of some 
disease-causing microbes (Russian). Wratch., 1890. No. 6, pp. 133-135. 
Russell; l. c 
Kornauth : (21) Ueber das Verhalten pathogener Bakterien in lebenden 
eben. Centrb. f. Bakt., Parasiten-Kunde, u, dnfectionsk, I Abt., Bd. 
— No, 21, 8 Juni, 1896, pp. 801-805, 
