___ be found elsewhere, 
64 BOTANICAL GAZETTE 
other kind of rust grows, and what was mere collecting has resolvei 
itself into an ecological study of absorbing interest. 3 
Only a rich and plentiful occurrence of the rust, whether over ) 
or restricted areas, is of much value to furnish a clue to relationship. — 
Scattering aecidia or teleutospores generally mean that the source 
infection is at a considerable distance, and what is found has come : 
chance spores blown long distances by the wind. Species vary muci 
as to the distance spores may be carried in condition to start infection, — 
but for our present purpose any distance from a hundred feet toam 
or more is likely to be enough to render our deductions very uncertail. 
Probably the easiest and clearest clue is obtained by watching i _ 
the first appearance of aecidia. If they can be found thickly covering 
Brass (or sedge) leaves, more abundantly upon those closé 
aecidia, and fewer the greater the distance. Only the earliest 50! 
be of value for our purpose, because uredospores germinate rea 
a tule, and give tise to uredosori that cannot be distinguis : 
ersees arising from aecidiospores. If such juxtaposition of the 
kinds of spore formation, such coinciding of two centers of int 
; sid or for more than one season, especially wh' 
| ee Oo BOL Occur ia & way to cause confusion, we are provi 
_ Strong clue to relationship. Of course, nothing short of cu 
. Suable One to be perfectly certain. A clue of this sort led t 
‘Sowing for the Aster aecidium mentioned above. a 
Such good fortune as finding the two halves of a rust | 
