Spore-Culture, 109 
been preserved, and according to the temperature of the 
atmosphere at the time the experiment is made. I never 
remember having seen any teleutospore germinate if the 
temperature within the bell-glass was below 5° C. Germina- 
tion is very partial and very slow at 8° C., but at from 10° 
to 15° C. it is both vigorous and rapid. The germination 
can be recognized to have taken place, if it be at all free, by 
the naked eye; the clusters of spores will then be seen to be 
surrounded by an opalescent, hazy cloud, which, when 
placed under the microscope, will be found to consist of 
myriads of promycelia. A very convenient method of 
preserving material on grasses—such, for instance, as Uro- 
myces poe, which occurs on the leaves of the grass that in 
the ordinary course of events become disintegrated by 
decay during the winter—is to gather a small bundle of 
affected leaves, attached to the stems, place this bundle in 
a flower-pot just as if it were a living plant, to cover the 
flower-pot with a bell-glass, and keep it out-of-doors in a 
shady place all winter. There will be enough moisture in 
the atmosphere to prevent the material from being injured 
by desiccation, but not enough to allow the teleutospores 
to germinate until they are purposely placed in water. 
The bell-glass will protect the grass from injury by wind 
and weather; so that when spring comes you will have 
abundance of material ready to hand, in excellent condi- 
tion for germination, which you can induce at pleasure, by 
merely soaking it in water. The same method may be 
conveniently adopted with those species which occur on 
leaves, and in which the spores are lost by their decay in 
the ordinary course of events. The Melampsore on willow 
and poplar may thus be kept out-of-doors under a bell- 
glass with great facility. 
With those species which occur on leaves of plants 
which have a very perishable foliage, it is necessary to 
