in the Brontes and their Brown Rust . 277 
germinated on the epidermis, or the infection has failed, owing 
to the germ-tubes being unable to enter the stomata and 
establish a mycelium in the intercellular spaces. 
At the other extreme we have successful entry and in- 
fection, and the mycelium in the leaf gives rise to the pustules 
of Uredospores in due course. 
Thirdly, we may have the intermediate stage where pale 
flecks betray the presence of a mycelium in the intercellular 
spaces, but circumstances prevent this coming to maturity as 
a spore-producing organism, and so no pustules of Uredo- 
spores are formed. 
Whether this internal mycelium 1 eventually lives or dies 
depends on several factors ; the point here is that it remains 
barren of spores. 
The fourth case is met with when the tissues turn brown 
and die, the destructive action of the infecting tubes having 
killed the cells too rapidly. The affected patch thus appears 
corroded, and since the dead cells are unsuitable as a medium 
for further growth of the mycelium, the parasite dies. 
In the following tables I record the infection as successful 
or positive (indicated by the sign + ) only when the spore- 
bearing pustules are developed at the infected spots. In all 
other cases it is unsuccessful or negative (indicated by the signs 
O or — ) and only when necessary is the remark added that 
the infected spots show ‘ flecks ’ or * corrosion ’ respectively. 
The histological details and figures are held over for the 
present, with other continuations of the work, and will form 
the subject of further communication. 
9. Experiments with Pot-plants. 
The first set of experiments of which I propose to give the 
results here, was simply planned to see whether seedling 
plants, of manageable size and in small pots, were suitable for 
the purposes of the investigation. The procedure adapted 
was as follows. 
Seedling plants of the species of Bromus referred to below 
1 Internal, that is to the leaf as a whole, but really in the intercellular spaces. 
