20 THE MYXOMYCETES 



Haller seems to have been the first to recognize the genus. Persoon 

 defined it more closely and illustrated it. Link merely translated the 

 name into Greek and in this was followed by Fries. 



The structure of the central sporiferous region is difficult to inter- 

 pret. It is commonly regarded as composed of tortuous, interlaced 

 sporangia, but it seems more reasonable to regard these bodies as more 

 in the nature of plasmodiocarps, representing the principal veins of 

 the Plasmodium which have matured without proceeding to the spo- 

 rangial stage. The walls of these bodies, whatever their nature, to a 

 considerable extent take the place of a capillitium and hence form a 

 pseudocapillitium in addition to the true capillitium formed within 

 them. 



The taxonomy of the genus is likewise perplexing. Are the various 

 forms simply phases of a single species or to what extent are they 

 sufficiently constant in their admitted variety to claim specific rank 

 and separate description? To follow the example of Greville and 

 recognize in all the literature of two centuries varied descriptions of a 

 single type — this were perhaps the easier and speedier disposal of 

 the case. Fries thought so to treat the problem but was unable to keep 

 faith with his own decision, for he no sooner states the genus mono- 

 typic then he proceeds to offer four varieties, the same as those recog- 

 nized by Persoon and others as species. More recent students seem 

 to find convenience in specific division, thus indicating that to careful 

 observers all over the world there are differences that may be and 

 have been recognized again and again. It will be said, was said by 

 Fries, that these variations are insignificant, "pendent ex aeris consti- 

 tutione"; but as a matter of fact the several types here described may 

 be found on the same day in similar habitats, so that evidently some- 

 thing other than atmospheric environment must determine their final 

 aspect. However it may be, there are many varying presentations of 

 Fuligo capable of illustration and description. Some of these forms 

 we venture to describe, with such annotation as may show something 

 of present knowledge. 



KEY TO THE SPECIES OF FULIGO 



a. Spores predominantly elliptical; fructification plasmodiocar- 



pous or sethalioid; crust white I. F. cinerea 



a. Spores predominantly spherical; fructification aethalioid; cor- 

 tex various b 



b. /Ethalia small, usually 1 cm. or less in diameter 2. F. muscorum 



b. y£thalia larger, usually 2 cm. or more in diameter c 



c. Spores mostly 6-9 n, always under 10 /z 3. F. septica 



c. Spores 1 1 n or larger d 



