132 TRANSACTIONS OF THE 
potassium nitrate, magnesium nitrate, sodium carbonate, 
potassium carbonate, sodium sulphate, potassium sulphate, 
and magnesium sulphate. 
The antagonistic effect of combined salts was not so 
great in soils as in solution cultures. 
The percentage of soil moisture influences the toxicity 
of alkali salts. 
Salts added to the soil in the dry state do not have so 
great an effect as those added in solution. 
Land containing more than about the following per- 
centages of soluble salt are probably not suited without 
reclamation to produce ordinary crops. In loam, chlorids, 
0.3 per cent; nitrates, 0.4 per cent; carbonates, 0.5 per cent; 
sulphates, above 1.0 per cent. In coarse sand, chlorids, 0.2 
per cent; nitrates, 0.8 per cent; carbonates, 0.3 per cent; 
and sulphates, 0.6 per cent. 
SOME UNIQUE RUSTS. 
The rust fungi include over two thousand species of 
parasitic fungi. The usual text-book in elementary botany 
uses Puccinia graminis or wheat rust as the type of these 
species—a rust probably as atypical as could be selected. 
In order that the references in this paper shall be clear, 
permit me to give a few elementary definitions. Rusts are 
either autoecious or heteroecious—an autoecious rust being 
one that has all of its spore forms on the same species of 
host plant, while a heteroecious rust requires two species of 
hosts for its life cycle. The complete life cycle of a heter- 
oecious rust is as follows: In the spring spores called 
aeciospores are produced in chains in a special cup-shaped 
spore-case (technically a peridium) called an aecium. 
These spores are blown to the alternate host, and there 
germinate, producing a mycelium (or rust plant) within 
the tissues of the host. Within a short time this mycelium 
fruits by producing clusters of one-celled reddish or brown- 
ish spores called uredospores. These blow to other plants 
of the same species, germinate and form new mycelia, 
which in due time produce their successive crops of uredo- 
spores, and so on all during the summer. The uredospores 
