vi] Rusts 71 
Remedial Measures. 
All attempts to check rust by spraying and treat- 
ment of seed have failed entirely. The cereal plants 
do not lend themselves to spraying as the nature of their 
leaves is not suitable for holding the spray, but rather 
the contrary. It is chiefly with yellow rust of wheat, 
as being the commonest, that work is being done to 
help the farmer. 
The susceptibility of wheat varies very largely 
among the different varieties. Some are practically 
immune, but these are either bad yielders or of poor 
quality. Biffen has found it possible to cross a heavy 
yielding variety susceptible to yellow rust with one that 
is immune and to pick out from the offspring a variety 
with the cropping power of the susceptible variety and 
the immunity of the other. 
Wheat immune to yellow rust may be susceptible 
to other rusts. 
On crossing a wheat which is susceptible to yellow 
rust with a variety which is immune from that rust, 
the whole of the plants derived from the seed produced 
are readily infected. On sowing the seed from these 
rusted plants it is found that although the majority 
of the plants produced are infected, about one-quarter 
of them are free from it. Of these a certain proportion 
possess the high yielding property of the original 
rusted parent together with the absence of liability to 
rust. 
On growing these wheats the plants produced are 
all practically immune from the yellow rust. In this 
way a wheat known as Little Joss was produced by 
crossing Square Head’s Master with a wheat immune 
