ATTITUDE OF PATHOLOGISTS AND BACTERIOLOGISTS. 15 
The English edition of von Tubeuf (1897) does not differ essentially from the German. 
Frank’s Kampfbuch, published in 1897, is chiefly interesting in this connection, because 
in it the author announces his changed views respecting the existence of bacterial diseases 
of plants. Concerning them we have the following very cautious recantation (p. 201): 
Whether bacteria can be the cause of disease in plants is always a question to be considered 
with circumspection. In case of the potato-rot this doubt was formerly so much the more justified 
because we had learned to know a genuine thread-fungus, the Phytophthora, as the cause of this 
disease, and consequently the suspicion at once arose that perhaps this fungus was really the true 
cause of the disease and might have paved the way for the entrance into the potato of the decay 
bacteria. I myself have held fast to this doubt until quite recently, but must give it up as a result 
of my own investigations recently instituted. 
In his Vorlesungen, published in 1897, Fischer takes the ground that there are no 
bacterial diseases of plants and can not be any for reasons cited, to wit, the bacteria can 
not enter the plant except through wounds, and their development in the latter is soon 
stopped by the formation under them of an excluding layer of cork. Stomatal infection 
is altogether impossible for the reasons stated: 
Die unverletzte Pflanze steht mit der Aussenwelt nur durch die Spaltéffnungen in offener Ver- 
bindung, die selbst sich darauf beschrankt, dass das gegen die Zellen ganz abgeschlossene System 
der lufterfiillten Intercellularraume mit der Aussenluft kommuniziert. Wenn durch den Wind oder 
durch Regen Bakterienkeime in die Spaltéffnungen gefithrt werden, so gelangen sie von hier aus nur 
in diese Intercellularraume, wo ihnen ausser dampfgesattigter Luft nichts weiter geboten wird, wo 
alle Nahrstoffe fehlen, ohne die keine Bakterienspore auskeimt, keine Bakterienzelle sich vermehrt. 
* * * Alle diese Fahigkeiten fehlen den Bakterien, gegen die eine unverletzte Pflanze vollkom- 
men geschiitzt ist. Aber auch die verwundete Pflanze wiirde nur in den gedffneten, verletzten Zellen 
Nahrstoffe fiir Bakterien darbieten, eine Quelle, die bald dadurch abgeschnitten wird, dass unter 
der Wundflache eine undurchlassige Korkschicht (Wundkork) entsteht, die jeden weitern Safteaus- 
tritt aus der Wunde verhindert. Die Wunde bleibt nicht feucht, die verletzten Zellen schrumpfen 
und trocknen ein und damit ist den Bakterien der Eingang genau so versperrt, wie an der unver- 
letzten Pflanze. Ihr drohen demnach auch keine Wundinfektionskrankheiten durch Bakterien, deren 
Weiterverschleppung in der Pflanze gleichfalls unméglich ist. 
The following is a translation of the entire paragraph: 
Exclusive of the tubercle bacteria whose wonderful relation to the Leguminosae has been 
described already (Vorl. X), no single example is yet known of bacteria which can insinuate them- 
selves into the closed living cells of a plant. The uninjured plant stands in open connection with 
the outer world only through the stomata, which connection is so limited that the system of air 
filled intercellular spaces connects with the outer world but is entirely closed to the cells. When 
bacterial germs are forced into the stomata by wind or rain, they here reach only into these inter- 
cellular spaces where nothing further is offered to them than vapor-saturated air, where all nutrient 
substances are wanting, without which no bacterial spore can germinate, no bacterial cell can 
multiply. Even when such bacteria as can dissolve cellulose (the methane bacteria) are brought 
into the intercellular spaces they can not nourish themselves here, and can not develop their pecu- 
liarity of dissolving the cell-wall. Consequently only those parasitic organisms can penetrate into 
the plant with results, whose spores have brought along with them sufficient nutrient substance so 
that they can germinate in pure water, so that they can overcome the lack of nutrient substances 
which they meet with at first, and can open their attack on the protective cell-wall at their own 
expense. This requirement is fulfilled by the spores of parasitic fungi, which with their reserve 
stuff push out a germ-tube, which now bores directly through the epidermis of the plant (potato 
fungus, Phytophthora infestans) or which first penetrates into the intercellular system through a 
stoma (rust fungi), and from here boring through the cell-wall, multiplies in the cells, or at least 
sends into them special side branches of its mycelium as sucking organs (haustoria). All these 
peculiarities are wanting in the bacteria, against which an uninjured plant is fully protected. But 
also the wounded plant offers food for bacteria only in the opened, injured cells, a source which is 
soon removed by the formation under the wounded surface of an impenetrable cork layer (wound 
cork) which entirely prevents any further flow of sap from the wound. The wound does not remain 
moist, the injured cells shrivel and dry out, and consequently the entrance of the bacteria is exactly 
so barred out as in the uninjured plant. Consequently, there is not the least danger of wound- 
