Tan. 20, 1923 
Cytological Study of Injection 
133 
reached the limit of its development and was shriveled and dead. * No 
haustoria were found. She concludes that— 
The facts seem to suggest that the death of the entering hyphae is not due so much 
to starvation as to some poisonous substance emitted by the cells. 
Also that— 
The entrance of a stoma by any germ tube is no index of the capacity of that 
germ tube to infect the leaf. 
Miss Marryat (ip) studied the behavior of yellow striperust, Puccinia 
glumarum (Schm.) Erikss. and Henn., on a susceptible and an immune 
wheat. The fungus on the immune host enters in normal fashion, but 
the hyphae soon become watery in content, have few nuclei, and form 
almost no haustoria. The host tissue soon shrinks and begins to break 
down and die. Attempts to form pustules result in tangles of hyphae 
often lying deep in the tissues, among which a few abortive spores may 
be formed. The reason for immunity is not known but may be due to 
toxins and antitoxins. 
Stakman ( 26 , 27) also made parallel studies of wheat stemrust on 
immune and susceptible varieties of wheat and also of oats inoculated 
with stemrust from wheat and barley, rye from orchard grass rust, and 
several others. The fungus on an uncongenial host enters as usual, and 
the first hyphae may be vigorous. 
Within a short time after the hyphae become closely appressed to the host-plant 
cells, there are usually unmistakable evidences of some deleterious influence upon 
the host cells (27, p. ig6). 
The plastids become irregular and are often clumped and soon become 
fainter, leaving a homogeneous, uniformly staining mass. Hyphae may 
grow past cells that escape injury. A part of a host cell may be destroyed, 
leaving the rest untouched. The harmful effect of the fungus may precede 
actual fungus invasion. The action is sometimes less sharp and rapid. 
The more resistant a form, the quicker are host cells and fungus killed. 
There seems to be a very definite antagonism between the immune plant and the 
parasite 
and— 
immunity and resistance, especially when very marked, are quite independent of 
the nourishment of the plan t (27, p. iq8 ) .The evidence would rather 
eem to favor the view that the whole problem is one of toxins in the host or parasite 
or, very probably, in both (26 > p. 46). 
METHODS 
The strains of wheat stemrust used in the studies here recorded were 
Puccinia graminis tritici I and III and a local strain found growing in 
the breeding plot in Berkeley. The varieties of wheat were Baart or 
Early Baart (susceptible); Kanred, chosen for its immunity from 
several strains of stem-rust ( 6, 20, and 23 ); and to a minor extent 
Mindum (semiresistant). The seed of Early Baart used in this work was 
grown in the cereal plots at Davis in 1919, and that of Kanred came 
from Hays, Kans., in 1917 (C. I. 5146), and from plants grown here later 
from that seed, and the Mindum is Minnesota 470. The seedlings were 
grown in the greenhouse, inoculated about the ninth day after planting, 
kept under bell jars 48 hours, and then set in cheesecloth cages. The 
different lots of seedlings of Baart were grown and fixed in October, 
