1900] MacBride, — The slime moulds 79 
the snowy reticulations of Déachea. It must be understood in all 
cases that the color of the plasmodium in the same species varies with 
the progress of development, the food-supply and perhaps for other 
reasons to us unknown. The tints are not inherent, but are due to 
the presence of particles suspended in the protoplasmic stream. A 
plasmodium accordingly often loses its characteristic color as it passes 
into fruit. 
Later in the season the plasmodia of the autumnal species begin to 
put in an appearance. The jelly-like whitish or greenish masses which 
later form our species of Stemonitis may be seen as early as July or 
August, but are most common in September. Probably not a linden 
tree falls to decay in our northern forests which does not bear at least 
one abundant crop of Stemonitis, certainly S. maxima Schw., and 
probably other species. The coniferous logs of Washington and 
Oregon, and doubtless of all our northern woods, bear quantities of 
Stemonitis in various species. Comatricha and Dictydium are common 
on logs of oak, while Diderma floriforme Bull. spreads its white or 
watery plasmodium inside oak stumps and forms its fruit in darkness, 
even sometimes in the ground. In the latter part of August and in 
September, the creamy plasmodium of Muci/ago is everywhere in 
evidence, streaming amid piles of rotten leaves, climbing the living 
stems of herbaceous plants, there to hang in curious foamy masses of 
clustered fruit, an inch or two in length, unmistakable. The whole 
Trichiaceous series may now be sought, some with watery plasmodium 
rounding up in sporangia, white as ivory (7: varia Pers.), then dull 
yellow, ochraceous, orange ; some with plasmodium scarlet, 7: decipiens 
Pers., or rosy purple as Arcyria denudata L., or coral-red as Hemi- 
trichia vesparium Batsch. In autumn too some of the most common 
Physarums are abroad with their plasmodia, on leaves, in wood-heaps 
everywhere, their fructifications on straw, on sticks, on every humble 
thing. Some species late in the year whiten, as if by frost, the earth- 
ward side of every fallen log, especially of aspen, linden, willow. 
Another autumnal form sure to be discovered is again one of the giant 
species, Enteridium splendens Morg. In some rocky damp ravine, on 
some barkless log, half rotten, we may discover a row of whitish or 
flesh-colored small cushion-like masses, perhaps a.half a dozen of them. 
Another day we seek the place again; the cushions have changed to 
umber heaps covered with shining film, within like tiny sponges packed 
with spores. 
