MORPHOLOGY AND TAXONOMY OF THE SARCODINA 449 



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

 lose walls. The myxamebae foregather in clumps on which the 

 sori originate. Typical genera: Guttulina Cienkowsky, Gutlulin- 

 opsis Olive. 



Family 3. Dictyostelidae Rostafinsky.— Here the fruiting bodies 

 are borne on simple or branched stalks formed by the hardened 

 bodies of amebae which have migrated from the pseudoplasmodium 

 mass. The polygonal bodies, covered with cellulose membranes, 

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

 at the top or at the ends of branches (Fig. 185). The myxamebae 

 are characterized by thin, pointed pseudopodia. Typical genera: 

 Dictyostelium Brefeldt and Polyspondylium Brefeldt. 



Order II. PHYTOMYXIDA Schroter. 

 (Phy tomyxinae 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. They 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 brassicac 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. (See p. 38(3.) 



Other genera parasitic on plants are Tetramyxa Goebel (forming 

 galls on Ruppia rostellata) and Sorosphaera Schroter (causing tumors 

 in various species of Veronica). 



The genera Sporomyxa Leger and Mycctosporidhnn Leger and 

 Hesse are parasites of beetles (Scaurus tristis and Otiorhynchus 

 uscipes) . 



Order III. EUPLASMODIDA Lister. 

 (Mycetozoa s. str. Myxogastres). 



This order includes the great majority of Mycetozoa which in 

 their life histories agree with the description given above (p. 445). 

 Myxamebae and myxoflagellates are invariable, so too are true 

 plasmodia and complex sporangia which with the exception of the 

 family Ceratiomyxidae (Exosporea) are invariably surrounded by 

 a peridium. 



The "spores" are usually globular, rarely elliptical, and are often 

 compressed by pressure into polygonal forms. In the majority of 

 cases they are violet in color but colorless, white, yellow, brown and 

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