Dec. 22, 1923 
Cytology of Wheat Stem Rust 
599 
of salts, bases, organic acids, and carbohydrates. There was no response 
to inorganic acids nor to some organic compounds. Unrediniospores of 
Puccinia porri ger m inating on the surface of a bulb scale induced positive 
chemotaxis in the cells below. 
Nestler (27) obtained positive traumataxis in a wide variety of plants. 
Sie wurde bei Monocotylen, Dicotylen und Algen beobachtet und kommt in 
■analoger Weise bei Blatt-Stengel-und Wurzelorganen vor. 
So, in the flowing of living protoplasm towards the fungus in Mindum 
and in the other cases cited, we are dealing with a reaction common to 
many plants and capable of being elicited by a great variety of stimuli. 
There is another angle from which this question can be viewed. The 
protoplasm of the host moves towards and surrounds the haustorium. 
Both the cytoplasm involved and the haustorium die. This process may 
be remotely akin to phagocytosis. Kolmer (20) , speaking of the inges¬ 
tion of the bacteria, in an infection, by the phagocytes, says, ( p . 181 ): 
As a rule, chemical stimuli serve to attract cells to the site of infection, thus consti¬ 
tuting what is known as positive chemotaxis. 
Again (p. 183)— 
In bacterial infections the toxins, and especially the protein of dead microorganisms, 
are regarded as mainly responsible for the occurrence of positive chemotaxis. 
And further ( p . 184 )— 
Thus Metchnikoff has asserted that leukocytes might, after a time, be attracted 
toward substances that would kill them. Therefore, while leukocytes will migrate 
freely toward substances that would kill them, they may be destroyed before they 
reach the inflammatory area, or, having reached there, are promptly destroyed and 
pass into solution. 
Of course, the differences between phagocytosis and conditions in rust 
parasitism are great. We are not even dealing with a free motile cell. 
The mechanics of the motion toward the invader may be different. The 
surface tension theory of phagocytic motion might possibly be applicable 
to the motion of the nucleus, but it would be difficult to apply it to the 
flow of cytoplasm in a cell with fixed boundaries. This much they have 
in common, however, whether it be significant or not: The host substance 
moves towards the foreign organism and the toxin emanating from it and 
flows around it, even though killed by it. 
This toxin which proves fatal to Mindum protoplasm probably is se¬ 
creted by this same rust in the other hosts, but it produces very different 
results there. Occasionally the nucleus is found alongside of a haustorium 
in Kanred, and there may be an initial flow of cytoplasm toward the 
haustorium, but, if so, it is inconspicuous and there is later a recovery 
from it. When form XIX grows on Kanred (type of infection o) the 
host nucleus often is near the fungus. 
The nuclei in infections in Kanred and Baart increase greatly in size. 
This was not so marked in Mindum, for the nuclei near the fungus are 
killed, but farther out there is slight expansion. Eriksson (jj, pt. II) 
noted nuclear enlargement in Puccinia dispersa Erikss. in young infec¬ 
tions on rye: 
Der kern zeigt sich etwas vergrossert . . . 
And later— 
Noch starker zeigt sich indessender Hypertrophie des Kerns in der letzten Ein- 
legimg . . . unmittelbar vor dem Hervorbrechen der ersten pusteln . . . 
And— 
solche Hypertrophien auch weit von raycelienfaden entfemt vorkommen. 
