UTAH ACADEMY OF SCIENCES 133 
are the multiplying spores of the plant. In the late sum- 
mer or in the autumn, the same mycelium which has been 
producing uredospores now produces clusters of two-celled, 
thick-walled spores known as teliospores. Although in a 
few forms these germinate at once, in most forms they re- 
main on the plant during the winter, and in the early spring 
(about the time the alternate host has begun to leaf out), 
each teliospore germinates by producing from each of its 
two cells a tube called a promycelium. This promycelium 
cuts off four cells at its upper extremity, and from each of 
these cells develops a minute spore called a sporidium. The 
sporidium is blown to the host that produced the aecio- 
spores, and there germinates into a mycelium which gives 
rise to the aecia again. 
But we have many variations from the above typical 
life history. Some rusts never have the aecial stage; some 
never have the uredo stage; while still other species omit 
both of these stages, the spores that are produced being 
only sporidia and teliospores. Again, some do have all the 
stages when conditions are favorable, but can abbreviate 
their life-history if one of the alternate hosts is not available 
for infection. Wheat rust is a splendid example of this. 
In the study of the rusts certain general relationships 
have been recognized as existing in nature. The purpose | 
of this paper is to call attention to some departures from 
these. For example, it is believed in general that all the 
rusts on the grasses, rushes and sedges are not only heteroe- 
cious, but that they have their aecial stage on some 
dicotyledonous host. A striking exception to this is Puc- 
cinta graminella (Speg.) Diet. & Holway, found on Stipa 
eminens Cav., which produces its aecial stage on the same 
host as the teliospores, i. e., it is autoecious. But Puccinia 
graminella is unusual in another respect. All other grass 
rusts so far as known produce the complete cycle of spores— 
aecia, uredo and telial—but this species apparently does not 
produce the uredospores. 
Another unusual grass rust is the race of Puccinia 
found on Phalaris. These rusts produce their.aecia on a 
monocotyledonous host. 
