ARTHUR: PROBLEMS IN THE StTupy OF PLANT Rusts 15 
was found “on various species of grasses and sedges.’’ But such 
instances as these are not known at the present day. There is no 
species known that inhabits grasses avd sedges. Moreover, it is 
rare that any species of rust will be capable of growing on all the 
genera of a large family, or even on all the species of a large 
genus, unless these be remarkably homogeneous, 
Is it not apparent that the exact identity of the species of host 
on which a rust is found constitutes information for the proper 
study of its systematic relationship and often of its specific iden- 
tity only second to the characters drawn from the fungus itself? 
No rust can be considered apart from its host; the parasitism is 
so closely wrapped up in the evolution of the species that to ignore 
it would be folly. Many collections of Uredineae are rendered 
nearly worthless for study because the collector neglected to 
determine the host, or to include material in the collection by 
which the student could determine it. So little importance has 
been attached by collectors to this part of their work that rarely 
are characteristic parts of the host included, so that the student 
may independently satisfy himself of the correctness of the deter- 
mination, and so that in after years the determinations may be 
revised, if necessary. It is usually forgotten that the classification 
of phanerogamic plants has not yet become perfect, and every 
change in their nomenclature must be reflected in the nomencla- 
ture of the uredineous hosts. Evidences of the lack of apprecia- 
tion of the importance of correct determination of the hosts of the 
Uredineae are shown in many ways; I may cite an instance coming 
to hand while preparing this address. In an exhaustive treatise 
on the flora of the island of St. Croix about fifteen hosts are men- 
tioned for the few rusts that had been collected, and four of these 
are not listed in the phanerogamic part of the work. Again in 
that admirable flora of Alabama, issued some time ago, the life- 
work of Dr. Mohr, a number of uredineous hosts are mentioned 
not in any way referred to under the families of phanerogams 
where they should appear. Another source of annoyance and of 
misinformation is the not infrequent failure of uredinologists to 
recognize hosts under their synonymic aliases. It is very easy at 
the present time for a plant to go masquerading under several names. 
Of course, the well-informed ought not to be deceived by these dis- 
