July 15,1914 
Influence of Host on Puccinia 
319 
The modification of such profound morphological characters as shape, 
size, thickness, and markings of the walls of the spores by aecial or 
other hosts opens a broad and very important field for scientific research. 
It may prove to be the key to many anomalous conditions in the life 
history of the Uredinales which hitherto have appeared inexplicable. 
The practical importance of these facts in relation to rusts of economic 
importance, such as those attacking cereals, truck crops, fruit and forest 
trees, is evident. 
SUMMARY 
(1) Puccinia ellisiana has two widely separated aecial host genera, 
Viola and Pentstemon. 
(2) The infection of Pentstemon by Puccinia ellisiana is vigorous and 
abundant. 
(3) The characters of Puccinia ellisiana after passing through 
Pentstemon are entirely changed. 
(4) The new characters assumed by Puccinia ellisiana correspond in 
every essential feature to those belonging to the Pentstemon rust, 
Puccinia andropogonis, 
(5) The infection of Viola spp. by the ordinary Pentstemon rust, 
Puccinia andropogonis , also occurs. 
(6) The characters of the rust obtained by inoculating species of Viola 
with Puccinia andropogonis are those of the regular Viola rust, Puccinia 
ellisiana . 
(7) The transfer of Puccinia ellisiana from Pentstemon back to the 
Viola is much more difficult than that from the Viola to Pentstemon. 
(8) Puccinia andropogonis may easily have originated in nature from 
Puccinia ellisiana . 
(9) In the case of the rusts under consideration the determining 
factor as to the characters assumed by the spores is the aecial host. 
47531—14- 
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