4 Mycetozoa of North America 



sporophores, are of three kinds. (1) True sporangia, produced 

 by the majority of the species, are often in thousands of indi- 

 viduals from a single plasmodium, and are almost symmetrical 

 and uniform in shape and size. Most of them are small, averag- 

 ing in height about 1 mm., but in some species they may reach 

 15 to 25 mm. They may be sessile, or on stalks of varying 

 height, and exhibit great diversity in form, color, and structure, 

 among the different species. (2) Plasmodiocarps, produced 

 habitually by certain species, and frequently by others that nor- 

 mally produce true sporangia, are sporangiate in character, par- 

 ticularly in their internal structure, but are not uniform in shape 

 or size. The form may be extended in the linear direction many 

 times the height or breadth, and again curved, serpentine, ring- 

 or crescent-shaped. The form may be in thinly or thickly effused 

 masses, or there may be a netted structure with numerous meshes 

 or openings. In the latter formations the plasmodiocarps may 

 extend several inches. Plasmodiocarps usually are sessile; are 

 frequently produced in considerable numbers by an individual 

 Plasmodium; and occur often along with true sporangia in the 

 same fructification. (3) Aethalia. Here the entire mass of 

 Plasmodium forms one or a small number of fruiting bodies. 

 Aethalia are much larger, as a rule, than sporangia or plasmodio- 

 carps, and in some species a single one may be as much as a foot 

 across. The aethalium consists of confluent sporangia, the inter- 

 vening walls more or less developed or degenerate, and the whole 

 covered by a firm or fragile cortex or wall. 



The Mycetozoa require for their development a habitat of 

 decaying vegetable material with warmth and moisture and the 

 consequent growth of bacteria as a food supply. The plasmodia 

 thrive in decaying wood (preferably in the earlier stages of decay), 

 leaves, twigs, refuse and manure piles, and the ground, wherever 

 favorable conditions prevail, and travel through the crevices and 

 cavities in the search for food. The fructifications are produced 

 on the habitat or in close proximity thereto. The time for their 

 most prolific development in the northern temperate zone is in 

 the months from June to October inclusive, although they may 

 often be found in the other months, including those of the winter, 

 if weather conditions are propitious. The appearances are not so 

 abundant during long periods of wet or dry weather, but in the 

 first week or so of dry weather, after a rainy speli,^ they may be 

 expected plentifully. They may be sought for in- the most un- 



