1896.] The Bacterial Diseases of Plants. 629 
taceæ resisted until plunged under oil when they decayed 
quickly. Aquatics resisted: “By means of a Pravaz syringe 
I have injected a drop full of the spores of Amylobacter into 
the lacunary system of several submerged aquatics (Vallisneria, 
Helodea, Ceratophyllum) but always without result. The 
plant remained healthy in all its parts.” 
These papers of van Tieghem are often cited, but they have 
little substantial value. Undoubtedly he believed that he was 
experimenting with pure cultures, or, at least, that the results 
obtained were due to Bacillus amylobacter, but such is, to say 
the least, very improbable. B. amylobacter is now believed to 
be strictly anaerobic, and incapable of any action on cellulose.” 
More recently Julius Wiesner has divided all plants into two 
classes, ombrophobic and ombrophylic plants, according as 
they are or are not readily injured by prolonged rains or ex- 
posure to stagnant fluids.» His experiments show that the 
aerial parts of some plants rotted very quickly when exposed 
to continuous artificial spray while similar parts of other plants 
proved very resistant, remaining sound for weeks (62 days in 
case of Tradescantia guianensis). The same contrast was ob- 
served when leaves of the two sorts of plants were placed in 
stagnant water, the former lost their turgor and rotted ina few 
days, the latter proved much more resistant. Many land 
plants have this power of resistance and all water plants, also 
all underground parts, even the roots of plants having very 
susceptible foliage: As additional confirmation Wiesner states 
that when meat infusions are left to themselves they always 
decay much sooner than when fragments of ombrophylic 
plants are placed therein. _Ombrophobic plants in water or 
meat infusion also decay less rapidly when mixed with frag- 
ments of ombrophylic plants than when left to themselves. 
This decay is more rapid in the dark than in light, especially 
?Prazmowski: (6) Untersuchungen ueber die Entwickelungsgeschichte und 
Fermentwirkung einiger Bacterien-Arten, Leipzig, 1880, pp. 23-37. 
ê Wiesner: (7) Ueber ombrophile und ombrophobe Pflanzenorgane, Sitzungsh. 
K. Ak. d. Wissenschaften, Math.—Naturw. Classe. Wien., 1893, Bd. 102. Abt. T, 
pp. 21. See also Wiesner: (8) Pflanzenphysiologische Mittheilung aus 
Buitenzorg (III). Ueber den vorherrschend ombrophilen charakter des Laubes 
der Tropengewiichse. Jbid., 1894, Bd., 103, pp. 169-191. 
