490 Freeman. — Experiments on the Brown 
precede the sorus formation, is not always noted ; they may in 
some cases be due to other causes than the infecting Fungus. 
It happens very frequently that the tip of an infected leaf 
dries up. When this extends to or past the point of infection 
it is noted as * tip-dried.’ It is not a matter possible of exact 
determination how far the success of the infection is impaired 
in such cases. In many, pustules arise in the dried portions 
and in others below the point of infection. Those cases only 
are noted where it seems possible that the drying may have 
interfered with the growth of the Fungus. ‘Leaf dried’ de- 
notes that the whole leaf has dried up. The unusually large 
number of dried leaves in Experiment 84 and 85 was due to 
very low temperature and a too sudden exposure of the 
plants to external conditions after infection. 
When more than one leaf on a single plant shows pustules, 
it is in almost every case, without a doubt, due to a falling of 
spores from the infected leaf on to the leaf below ; such are 
not included in the totals. Occasionally, pustules are reported 
and subsequently lost ; this may be due to one of two reasons. 
First, the infection material may, when in bulk, simulate 
a sorus, even under a lens, and the error may not be detected 
until a later examination ; and second, the leaf may become 
dried, and if the pustule is small the latter may disappear. 
Leaves ‘ missing ’ have been cut off by slugs or accidentally 
torn off in handling. 
Each experiment was continued about three weeks ; the 
incubation period of about twelve days prevents a second 
infection from the earliest pustules. 
The following tables summarize the results. They include 
those plants with ‘dried tips,’ &c., which were possibly in- 
capable of forming pustules so that general averages only 
must be reckoned. 
Series A gives twenty-two species. In 11, 12, and 19, and 
also in 15 and 16, the number of plants worked with is too 
small for generalization. The same applies to several species 
included in the following series. In B. pitensis and B. nnio- 
loides large yellowish flecks were very easily produced but 
