IOWA ACADEMY OP SCIENCES. 
37 
United States. Colorado and Southern California have 
characteristic species. 
It is, therefore, with surprise that I present here a list of 
species in nearly all respects such as might be gathered in 
almost any grove in eastern Iowa. 
This is the more remarkable when we discover that the 
phenogamous species of the locality in question are nearly 
all western or southwestern; scarcely one, unless, per- 
chance, some introduced weeds or possibly some of the 
grasses or composites, is characteristic of the flora of the 
northwestern United States or of the upper Mississippi 
valley. We have Pinus ponderosa^ P intis edulis, Pseu- 
dotsuga douglasii, Abies concolor; we have southwestern or 
western oaks, junipers, barberries; among the trees, only 
the quaking asp is familiar to our northern eyes. 
Now it must be further said that the quaking aspen, 
with its soft, rapidly decaying wood, affords here in Iowa 
a favorite habitat for many of our slime-mould species, and 
the same thing is true on desert mountain-tops. I found 
fallen trunks of Populus wet throughout, the rotten wood 
enclosed by the unbroken bark and supporting abundant 
and varied plasmodia. The fallen trunks of Pseudotsuga 
and Abies were also covered with traces of the minute 
organisms. 
The conclusion to be drawn is perhaps this: the Myx- 
omycetes being reproduced by minute spores are dis- 
tributed by the prevailing currents of the air. During the 
season when the spores are exposed for distribution easterly 
and southeasterly winds prevail; in the winter, when 
northern and northwest winds obtain the species of Oregon 
and Washington are deep buried in snow. This might 
account for what we And on the assumption that the dis- 
tribution is comparatively recent. 
It seems to me, however, that we must take a wider 
view. The forests of the desert mountains are remnants: 
they are the survivors of a forest probably at one time 
continuous, possibly both east and west. Perhaps at one 
time the meteoric conditions that support the forests of the 
