26 



ordinary one Is in numerous, small sporangia, either sessile or 

 with stalks, quite uniform in shape and size, and averaging a 

 millimeter or so, although in some species they are larger and 

 may reach a height of 20 mm. Another form is in plasmodio- 

 carps. These are sessile sporangia of irregular shape, sometimes 

 thinly and rather widely effused, or stouter and much elongated, 

 curved, sinuose or in rings. Again they may be branched or 

 netted, the last sometimes covering 20 sq. cm. or more. The 

 third form is in aethalia, which are compound bodies formed by 

 the union of many sporangia and with the walls of the compo- 

 nent sporangia more or less imperfectly developed. Aethalia are 

 usually sessile, and of large size, from about 1 cm. to 30 cm. 



The Mycetozoa are classified on the characters of the fruit- 

 ing bodies. More than 50 genera with about 400 species are 

 generally recognized. Obviously, all of them cannot be men- 

 tioned in the limited space of this paper — nor can they be fully 

 described — so that only a certain number of the common forms 

 have been selected. The student is likely to find others that 

 cannot be reconciled with the meagre descriptions, and if a small 

 portion, properly boxed and with data, is sent to me, I will be 

 glad to determine it and give any advice desired. The specimen 

 will not be returned. 



The higher classification into families, orders, and so on is 

 based on broad, general characters which are herein applied to 

 the genera described, and are present in all species of the genera, 

 whether mentioned or not, unless otherwise stated. 



Form of fructification. Fuligo, Tubifera, Enteridium, and 

 Lycogala form rather large aethalia with one or two exceptions 

 not mentioned. In all other genera described, except Ceratio- 

 myxa, the fructification is always sporangiate or plasmodio- 

 carpous. 



Spore color. In all genera Nos. 1-12, Badhamia to Lampro- 

 derma inclusive, the spores have some shade of violet-brown or 

 purplish-gray when observed through the microscope by trans- 

 mitted light with a magnification of about 600 diam. In all 

 other genera described, the spores have no purple tints, but are 

 yellow, reddish, olivaceous, or colorless. There are some excep- 

 tions in each group which are mentioned when the species are 

 covered in this paper. Spore color, size and markings are im- 

 portant specific distinctions between many species. 



