Feb. 9, 1924 
Resistance of Wheat to Puecinia graminis tritici 
399 
Bolley (7), Farrer (13), and Cobb (8) state that wheat varieties with 
stiff, upright growth and narrow leaves are less susceptible to P. triticina 
than are those with broader leaves and less erect habit of growth. Here, 
again, the germ tubes may have been prevented from entering on account 
of the failure of the stomata to open. The morphological characters 
pointed out by Cobb and others can be produced in any variety when 
it is grown under extreme conditions of soil fertility. 
Harter (20) found that wheat plants grown in soils to which had been 
added from 0.7 to 1.4 per cent sodium chlorid developed a heavy bloom 
on the leaf surface, thickened cuticle, and epidermal cells of reduced size. 
This condition may not have resulted from any physiologic action of the 
salt itself within the plant tissues. These xerophytic characters, to¬ 
gether with decreased transpiration, probably are due to the influence 
of the salt on the entrance of other soil nutrients; and, consequently, 
only a very poorly balanced nutrition is available to the plants. 
It appears from Table VIII that excessive nitrogen rendered plants 
more subject to attack*by stem rust. After inoculation these plants 
were kept in a saturated atmosphere and consequently the leaves were 
covered with a film of moisture. Iljin (26) concludes from his experi¬ 
ments on the transpiration of wet leaves that immersion in water in the 
dark has the tendency to cause closure of the stomata. However, if 
potassium nitrate is present in the water, the stomata open. 
Many investigators have shown that under certain conditions the 
amount of nitrate in the leaves of a plant supplied with an excess of 
this salt may be proportionately higher than in normal plants. Whether 
this condition can be associated with the findings of Iljin has not been 
determined. 
Rust appeared only on plants in the nitrate series. It is possible that 
the environmental conditions during the incubation period of the series 
of January 29 were such that the stomata of all the plants except those 
growing in soil with high nitrogen content remained closed. This sup¬ 
position is supported by the fact that, although the spores germinated 
profusely and abundant appressoria were formed on all plants, no flecks 
appeared on any of the plants which received no nitrogen, indicating 
that the lack of infection more likely was due to failure of germ tubes 
to enter than to any induced protoplasmic resistance. This explanation 
is partly confirmed also by the behavior of the plants in the second series. 
Here all plants became infected except those in series 125, which were 
grown in soil deficient in nitrogen. These plants were maturing early, 
the leaves were narrow, the stems upright, stiff, and provided with 
abundant bloom. The leaves, particularly, were rough and dry to the 
touch. 
Morphology of Host as Influenced by Nutrient Salts 
In order to compare the morphology of plants of Haynes Bluestem 
wheat grown under different conditions of nutrition, sections of the 
leaves were cleared and stained with Pianeze stain. Four such sections 
are shown in Plate 2, K, L, M, and N. Here, L and N show typical 
sections of a leaf from a plant grown in abundant nitrogen, not balanced 
by other nutrients. The epidermis is composed of very large, thin- 
walled, noncutinized cells. There is very little sclerenchyma, and the 
fibers do not extend from one leaf surface to the other. The intercellular 
spaces are very large, the leaf being porous and succulent. Plate 2, K 
