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darker otherwise. The capillitium is lax, not persistent, and 

 there is no columella. P. nielleuni is globose and yellow, with a 

 lax capillitium, a white or yellow stalk, and a short columella. 

 The stalk is densely calcareous and the lime-knots are large, 

 white or yellow. P. cinereum forms sessile sporangia and elon- 

 gated or branching plasmodiocarps, ashen-white in color. It is 

 distinguished from related species by the globose paler spores 

 which are almost smooth. P. sintiosum forms sessile, laterally 

 compressed sporangia and elongated, sinuose or branching plas- 

 modiocarps, similarly compressed. The color is white to grayish 

 or bluish, and the sporangium splits at the top or ridge to dis- 

 seminate the spores. 



Genus 3. FULIGO 



The fructification is always in sessile aethalia, the component 

 confluent and interwoven sporangia being similar internally to 

 the individual sporangia of Physarum. The common species is 

 F. septica which forms large masses, sometimes a foot across, 

 and usually of a yellow color. Occasionally the color runs to dull 

 red or brown, and a white phase in small aethalia is fairly com- 

 mon. The last appears much like F. cinerea but may be dis- 

 tinguished by the spores. In F. septica these are globose, 6-8a£ 

 diam. In i^. cinerea they are larger, darker, ellipsoid or subglo- 

 bose, and more strongly spinulose. Lime in granules is present 

 in Fuligo. 



Genus 4. CRATERIUM 



The capillitium is like that of Physarum but the six species 

 are separated therefrom mainly on the goblet-shaped or funnel- 

 shaped, stalked sporangia which have more or less distinct lids. 

 These lids open, and after the spores are dispersed, leave the 

 empty sporangia standing. There are exceptions, of course. The 

 common species is C. leiicocephalum and its variety cylindricum , 

 with sporangia white at the tops, ranging to reddish at the bases 

 and stalks. The variety is more cylindrical in shape. In both 

 the lid is white, convex, and crumbles away; the capillitial lime 

 is usually white, but may be yellow. The next ally is C. minu- 

 tum, which, in the common phase, is uniform in its brown color, 

 and has a lid depressed below the edge of the rim. The lime-knots 

 are white which distinguishes the species from C. concinnunt, 



