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Gelehrte Gesellschaften. 
production of secondary sporidia serves as a furthcr means of dis- 
semination. 
Having fallen upon a proper host, the sporidia produce the next 
phase of development by germinating, and entering the tissues of its 
leaves, fresh shoots, or fruit. A slight discoloration of the part af- 
fected ensues, followed by the production of flask-shaped cavities 
opening upon its surface known as spermogonia, within which are 
formed minute bodies, the spermatia, of doubtfoul function. These 
spermogonia are usually accompanied by bright orange discolorations, 
and by the secretion of a viscous saccharine substanoe attraelive to 
insects. 
The next step in development consists in the formation of aecidia, 
which appear upon the under surface of the leaves directly opposite 
the spermogonia, or in the same position with them if the part affected 
is a young shoot or fruit. The aecidia are cup-shaped bodies, within 
which numerous spores are produced successively, being pushed out 
in a mas surrounded by a membranous envclope, the peridium. By 
the rupture of this membrane the spores eseape, and, carried by the 
wind to a proper host, produce upon it the Gymnosporangia from 
which they were originally derived. This completes the round of 
development, which may be summarized as follows : the Gymno- 
sporangia on cedars produce spores (teleutospores), and these 
in turn produce sporidia, which, falling upon various Pomeae, result 
in the formation of a Boestelia, producing aecidial spores, which serve 
to reinfect the cedars with Gymnosporangia. 
To trace this Connection directly by actual experiment under test 
conditions was the object of the present cultures, and for this purpose 
seedliugs and older plants of the following species were employed, viz. : 
Crataegus tomentosa and coccinea, Pyrus malus, arbuti- 
folia, and Americana, with Amelanchier Canadensis. The 
plants were potted in most cases before the leaves were developed, 
towards the end of April, and kept in my rooms in Boston until the 
middle of July, at which time the more important results of the experi- 
ments had been reached. The locality was especially favorable for 
the purpose, being some miles from the nearest cedars, and this, together 
with the fact that only such leaves and shoots were infected as had deve- 
loped after the plants were brought to Boston, went far to diminish 
the chance of accidental infection from outside sources. 
Four rooms were at my disposal, and it was thus possible to guard 
against any mixture of the Gymnosporangia employed. A number 
of control plants were also used, and, by making the intervals be- 
tween successive sowings sufficiently great, plants subsequently infected 
were made to serve a similar purpose. The Gymnosporangia 
used included all the species found in this vicinity; namely, macro- 
pus, cl avar i a e f or m e , globosum, biseptatum, Ellisii, 
clavipes, and conicum. All of these, with the exception of 
Ellisii, matuve at about the same time, generally during the first 
week in May; and a supply of branches bearing the distortions pe- 
culiar to the various species was gathered in April, before the spori- 
