GYMNOSPORANGIUM WITH REPEATING SPORES 
41 
groups when Gymnosporangial aecia were found on the Rosaceous 
host Porteranthus,^ a herbaceous plant somewhat of the habit of 
Agrimonia. This species was G. exterum. The gap was next nar- 
rowed by cultures of G. speciosum on Philadelphus,^ belonging to the 
Hydrangiaceae, and the latest advance was made by using telia of 
G. Ellisii and growing aecia on the far more removed host genus 
Myrica,^ belonging to the family Myricaceae. 
So far as the aecial stage is concerned a complete alliance between 
the two groups of rusts has been established, shown in both morpho- 
logical structure of the fungus and relationship of hosts. So far as 
the telial stage is concerned no species has yet been found in which 
the initial diagnostic characters of gelatinized pedicels and Juniper- 
aceous hosts do not occur; that is to say, no advance has been made 
on the telial side in joining the two groups of rusts. 
We now turn to a consideration of the curious lack of a repeating 
stage. It might be inferred that the occurrence of the sporophyte 
on gymnospermous hosts indicates an ancient segregation of the 
group, which during a long course of specialization has dropped out 
the repeating stage. Furthermore, there may be something inhibitive 
in the nature of the gymnospermous host, although it would be 
difhcult to guess what it might be. Or, the long-lived sporophytic 
mycelium, often persisting for many years and never quite annual, 
may have rendered the repeating stage unnecessary, and thus led to 
its suppression. 
It has been suggested that the repeating stage occurs on the aecial 
host, being aecidioid, similar to that in Puccinia amhigua on Galium. 
The failure to find what might be considered secondary Aecidia, that 
is Aecidia unaccompanied by pycnia, seemed to negative this view. 
Nevertheless, more than one attempt has been made to infect the 
aecial host by sowing aeciospores, but uniformly without success. 
For some years an apparently genuine Uredo of the general form 
of that belonging to P. graminis has been known on a Juniperaceous 
host. In 1899 while on the Harriman Expedition to Alaska Professor 
Trelease obtained a small amount of what he named Uredo nootkatensis^ 
on Chamaecyparis nootkatensis, the yellow or Alaska cedar of the 
5 Arthur, Cultures of Uredineae in 1908. Mycologia i: 253. 1909. 
^Arthur, Cultures of Uredineae in 1911. Mycologia 4: 63. 1912. 
^ Fromme, A new Gymnosporangial connection. Mycologia 6: 226. 1914. 
^Trelease, in Alaska. Harr. Exped. 5: 36. 1904. 
