330 BIOLOGY OF THE PROTOZOA 



encysts and when a suitable medium is assured the small amoebte 

 again creep out, often, however, after a long period of desiccation. 

 Their characteristic ha])itat is animal dung. 



While many competent authorities regard these organisms as 

 remotely related, if at all, to the more complex Mycetozoa, w^e 

 believe that their affinities are more probably here than with any 

 other group of Protozoa. The three families recognized show 

 different gradations in complexity. 



Family 1. Sappiniidae, Dangeard.— The single genus and species 

 — Sajqnna jjedata, Dangeard— forming this Family differs from all 

 other Mycetozoa in that not even a pseudoplasmodium is formed, 

 a single amoeba going through all the motions of a Plasmodium. 

 Stalk and cyst are formed by one individual but the cysts are 

 frequently massed in sporangium-like groups (Fig. 147). 



Family 2. Guttulinidse, Cienkowsk3\— These are small forms 

 which bear stalked or unstalked fruiting bodies covered with 

 "spores." The latter have either thin membranes or heavy cellu- 

 lose walls. The myxamoebse foregather in clumps on which the 

 sori originate. Typical genera: (hdtulina, Cienkowsky, Guttulin- 

 opsis, Olive. 



Family 3. Dictyostelidse, Rostafinsky.— Here the fruiting bodies 

 are borne on simple or branched stalks formed by the hardened 

 bodies of amoebse which have migrated from the pseudoplasmodium 

 mass. The polygonal bodies, covered with cellulose membranes, 

 form a sort of tissue over which other amoebte migrate to form sori 

 at the top or at the ends of branches (Fig. 147). The myxama'bse 

 are characterized by thin, pointed pseudopodia. Typical genera: 

 Didyostdium , Brefeldt, and Polysijondylinm, Brefeldt. 



Order IL PHYTOMYXIDA, Schroter. 

 (Phytomyxin<e, Schroter). 



Probably as a result of parasitism peridia and capillitia are absent 

 in the representatives of this group. Otherwise they agree with the 

 more complex Euplasmodida. The^^ form true plasmodia and 

 myxoflagellates, but there are no closed sporangia, recalling in this 

 respect the simpler Acrasida. They are parasitic in plant cells and 

 in insects (beetles). 



Plasmodiophora brassicce, Woronin, is the best known of this 

 group largely because of its economic importance. It attacks the 

 roots of cabbages and other Cruciferae and produces a character- 

 istic tumor disease known as "Club-root," "Hanberries," "Fingers 

 and Toes," "Kohlhernie," etc. 



Minute flagellula" are formed from the cysts in an infected garden 

 and these, in some way, penetrate the root cells of the plant and 

 become myxamo^bse. The nuclei multiply and they grow in the cells 



