36 
IOWA ACADEMY OF SCIENCES. 
18. Lachnoholus occidentalis Macbr. 
19. Hemiirichia stipitata Massee. Typical; rare. 
20. Heinitrichia clavata (Pers.) Rost. Rare. The com- 
mon Mississippi valley form collected. 
21 Heniitrichia stipata (Schw.) Rost. Typical and fine: 
collected abundantly on fallen Populus. In fine condition 
in the last week of August. 
22. Physarum flavicomiim Berk. 
23. Trichia decipiens Pers. Typical, save that the spores 
are roughened and not reticulate as in the Mississippi val- 
ley. The spores correspond to those of European gather- 
ings. 
24. Trichia pers Not common. 
25. Perichaena corticalis (Batsch) R. Typical on the in- 
side of the bark of fallen trunks. 
The Myxomycetes or slime moulds are of world- 
wide distribution. As we regard them, they are an 
ancient group which, notwithstanding extreme sim- 
plicity of structure, has broken into all sorts of species 
and forms. There are some four or five hundred of 
these curious organisms known, and it is safe to say that 
no other group of equal size could easily be selected in 
which the species are as a whole more definitely limited 
or defined. They are variable^it is true, but not more so 
than lichens or asters or oaks; the difficulty lies in the 
fact that their variations all lie on the stage of our micro- 
scopes and are recognizable only under the best lens that 
our factories may supply. 
Notwithstanding this world-wide distribution it still 
appears that species have their individual range; not all, 
by any means, are cosmopolitan. The continents have their 
characteristic species, even genera as we now reckon them. 
There are forms in the Maine woods that have not yet been 
seen on our Iowa prairies nor in the forests of our valley; 
there are types in Oregon and Washington elsewhere un- 
known and many there which correspond to those of west- 
ern Europe more closely than to those of the eastern 
