43 
distribution and the kinds of slime-molds which occur. Some 
species are very adaptable, while others are found only on a 
few species of wood. In general, certain species are found on 
conifers, and certain other species on the broad-leaved trees. 
Badhamias show a distinct preference for aspens and cotton- 
woods, while the cribrarias are found mostly on conifers. 
Certain species occur on decaying logs on steep, relatively dry 
hillsides. Several species of Cribraria and Arcyria, and Stemonitis 
fusca and Comatricha nigra are frequently found in such places. 
These forms secure their moisture from melting snow, and ap- 
parently thrive at a lower temperature than most species. In 
these locations the sporangia appear in connection with a definite 
type and stage of decay. They have usually been found on logs 
of some size, where fungi have destroyed the lignin of the cell 
walls. So far no sporophores of these fungi have been observed 
and the causative organism is still in doubt. 
Certain aethalial forms—Lycogala flavo-fuscum and Mucilago 
spongiosa var. solida—have been found in situations which re- 
quire a different explanation. These occurred on the trunks of 
Street trees in Fort Collins, the former on living, the latter on 
dead, but still standing trunks of cottonwoods. These aethalia 
were from two to ten feet above the ground. In both the dead 
and living trees heart-rot had made considerable progress. Ob- 
servation showed conclusively that the plasmodium found both 
its food and the necessary supply of moisture in this heart-rot, 
“merging from cracks in the bark to form the aethalia. 
Evaporation from all exposed moist surfaces is very rapid 
throughout the district. This results in a further limitation of 
currence, and in frequent arrested development at various stages 
of the cycle. In most cases the length of the plasmodial stage is 
shortened and the colonies in all but exceptional cases are small. 
The €xceptions noted were largely colonies of Badhamia magna 
and Trichia decipiens, in a season when almost daily rains in a 
Particular locality continued for several weeks, checking the 
enon in a marked degree. This shortening of the plasmo- 
= Stage is also evidenced by the frequent occurrence of small 
poo and the very rare occurrence of larger ones. Rather 
“quently one meets with half-formed sporangia and aethalia. 
stil co sporangia have the usual shape for the species, ae ni i 
ing ae by plasmodial strands, the whole complex reta : 
color of the plasmodium, but having the texture 0 
