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In older to test the constancy oi physiological immunity the author
cultivated a number ol varieties oi wheat, different in their susceptibility
to brown rust
(P . trilicina)
in dillerent parts of Russia, in different condi
tions ol climate and soil in Middle Russia (Moscow, Vladimir), in South
Russia (Kharkov, Poltava), in Eastern Russia (Saratov) and in Turkestan
(Tashkent). In all these districts the brown rust is the predominant fust
species on wheat. In all these dillerent localities diflerences ol varieties
in relation to this rust proved to be quite similar. All varieties immune
to this rust in Moscow proved to be immune in South and East Russia
as well as in hot Turkestan *).
As to the influence of different factors of environment: temperature,
humidity, quality ol soil,etc., there is a great dilference of opinion (Compare
C o m e s, S t a k m a n, 177, V i l m o r i n , 196. G e n e s t e, 55,
Ga s s . n e t , 64, В i ! J e n. S p i n к s, 175, etc.).
The author’s experiments with the influence ol manure on immune
and susceptible varieties ol oats and wheat, the data of which are given
partly in his other work (1. c .)t partly in this book (see Tables 7, 8,
pp. 102—103) proved that even a high quantity of NaN03 (800 kilg. pro
hectar) could not change an immune variety into a susceptible one.
The difference of opinion on this subject is explained probably by
confusing the apparent greater liability ol attack bv fungi and bacteria ol
manured (by NaN03 and dung) plants with real susceptibility—as asotic
manure usually lengthens the period ol vegetation, i. e. the period of infe
ction, makes the leaf surface larger and consequently more attackable by
parasites. Yet here is no change ol plant reaction, no change of immunity
into susceptibility and vice versa, but only a more favourable influence
on the parasite itself.
Plnspliatic manure can sometimes shorten the period ol vegetation
and consequently shorten the period of infection, but again it does not change
the reaction of the plant itself.
In the majority of cases experiments have been made with susceptible
varieties, but it would be more convincing in order to prove the chan
geableness ol plant reaction to experiment simultaneously with the im
mune as well as with susceptible varieties.
The possibility of a change in the reaction of a plant to the parasite
is however not excluded. Thus Mr. S p i n k s noticed that salts of Li
diminish tlri susceptibility of wheat to mildew
(Erysiplie yraminis)
andl
l) As to the dilference in specialisationof Puccinia graminis f. sp. avenae, f. sp.
Iritici and (. sp. secatis in different countries,which is stated by investigations of Eriksson
{Swedenj, Jachevski (Russia), Carloton (N. America), Butler (India), Evans (S, Africa),
MacAlpine (Australia) and Gassncr (S. America), it is quite possible there may be diffe
rent races of this fungus in different countries, and this is very likely as this species is
very polymorfous (Freeman), and as in other species of cereal rusts there is no such diffe
rence in specialisation in different countries, tiassner (6H, 64) indicates another explana
tion of this difference; as a result of difference in methods; of inoculation used by diffe
rent investigators: namely the great influence of the qge of plants, when the inocula
tion was made.
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