74 



PLASMODIOPHORALES 



by research workers. Doubtless, there are numerous 

 other plasniodiaceous organisms wliicli resemble the 

 true Plasmodiophoraceae and simple fungi which 

 must eventually be given serious consideration by 

 mycologists and protozoologists, and it is hoped that 

 by presenting the available data here greater inter- 

 est and research may be stimulated in these border- 

 line organisms. 



SPOROMYXA 



Leger, 1908. Arch. Protistk. 12: 111. 

 (plate 13, fig. 1-25) 



Sporomyxa was created by Leger for a virulent 

 parasite, S. Scauri, which he found in tlie coelome of 

 the imago of Scaunts tristis in Algeria. The parasite 

 has a predilection for the adipose tissue and may be 

 found in enormous numbers there. Unlike most plas- 

 modioplioraceous fungi, it destroys infected cells 

 completely without stimulating them to divide or 

 enlarge. The earliest known stage consists of a small, 

 naked, spherical, ovoid. 6—8 /j.. or spindle-shaped 

 body with an unusually large, 5 /a, nucleus and finely 

 granular cytoplasm (fig. 1). It does not appear to 

 have a sharply defined membrane and lies embedded 

 in the host cytoplasm. As it increases in size the nu- 

 cleus divides mitotically with an intranuclear spin- 

 dle (fig. 2), and tlie thallus becomes binucleate. In 

 this stage it may divide by binary fission (fig. 3). 

 Additional nuclear divisions occur (fig. i). and 

 larger, naked, multinucleate plasmodium-like thalli 

 are eventually formed (fig. 6). Leger found no thalli 

 with more than 8 nuclei, and he believed that from 

 this stage on the parasite undergoes schizogony into 

 uninucleate meronts or sporulates, so that thalli with 

 a large number of nuclei are never formed. 



The mature thallus may be splierical, elliptical, 

 and sometimes amoebiform, according to the jiosition 

 its occupies in the host tissue, and although it may 

 have the shape and appearance of an active amoeba, 

 it does not move or undergo changes in form. Its cy- 

 toplasm is denser toward the center, but no distinct 

 endo- and ectoplasmic laj'ers are distinguisliable. 

 No wall or membrane is present, and the whole thal- 

 lus may be enveloped by the host protoi)lasm (fig. 6). 

 In addition to these thalli, Leger found otiier smaller 

 ones with numerous fat globules and chromatic gran- 

 ules in the cytoplasm and small nuclei which ap- 

 peared to be lacking in chromatin (fig. 7). He be- 

 lieved such thalli occur at the close of the vegetative 

 phase of iS'. Scauri and mark the beginning of sporo- 

 genesis. 



Unlike the true plasmodiophoraceous genera, no 

 segmentation of the multinucleate thallus into nu- 

 merous separate spores or cystosori lias been ob- 

 served in S. Scauri. Resting spores, however, occur 

 very abundantly in the adipose tissue, but Leger was 

 not certain whether they are formed by eneystment 

 of vegetative uninucleate thalli or are the products 

 of more or less simultaneous schizogony of a multi- 

 nucleate body. He admitted the possibility of both 



methods, but did not sliow any figures of the latter 

 process. The spores may sometimes occur in groups, 

 but it is not evident that these aggregates have been 

 formed by segmentation of a multinucleate Plasmo- 

 dium as in Plasmodia phora. The only developmental 

 stages of resting spores described by I-eger relate 

 to small, isolated spores. These are apparentlv 

 formed by the eneystment of uninucleate thalli dur- 

 ing which process the nucleus shrinks in size as chro- 

 matic material is extruded from the nucleole into the 

 cytoplasm (fig. 9-13). As this goes on, the wall 

 thickens and differentiates into a thick outer and a 

 thin inner layer. In bi- and multinucleate tlialli, 

 spore formation may be accompanied by nuclear 

 fusions (fig. 12. 13) of the type described by Prowa- 

 zek (0.5) for P. Bras.iicae. Leger interpreted these 

 fusions as representing rudimentary sexuality. The 

 majority of spores are ovoid, 8X 10 M> but they may 

 often be more elongate, iXS/i. spherical, obpyri- 

 form, constricted in the middle, and unusually large, 

 SO-iO /x (fig. 15-17). The small spores are usually 



PLATE 15 



Sporomi/x(t Scanri 



(All figures after Leger) 



Fig. 1. Uninucleate thalhis. 



Fig. J. Mitosis witli intranuclear spindle and minute 

 chromosomes. 



Fig. 3. Binucleate thallus undergoing binary fission. 



Fig. 4. Mitosis in a binucleate thallus. 



Fig. 5. Tetranucleate thallus. 



Fig. 6. Large, amoebiform, eight-nucleate thallus witliin 

 host cell. 



Fig. 7. Thallus with chromatic granules in cytoplasm; 

 nuclei without (?) chromatin. 



Fig. 8-1:3. Successive stages in resting spore formation. 



Fig. 13, H. Xuclear fusion (?) in resting spore. 



Fig. 15-17. Large, abnormal resting spores. 



S. Tertehronis 

 (All figures after Reitschel) 



Fig. 19-30. Developmental stages of thallus. 

 Fig. 31. Synchronous nuclear division; polar and profile 

 views. 



Fig. 22. Completion of cleavage into spore rudiments. 



Fig. 2S. Later stage of same. 



Fig. 2i, 25. Uni- and binucleate spores. 



f'i/.s'/o.s'/iora hfitntd 

 (All figures after Elliott) 



Fig. 30. Resting state. 



Fig. :37. Amoebae. 



Fig. 38-33. Nuclear division and multiplication. 



Fig. 33. Sixteen-nucleate stage of thallus; nuclei of un- 

 equal size. 



Fig. 3+. Migration of plasmodium through rootlet. 



Fig. 33. Cells of host with amoebae and plasniodia. 



Fig. 36. Root tip cells with plasmodium and amoebae; 

 nuclei of unequal size in plasmodium. 



Fig. 37-41. Stages in cyst formation from a plasmodium. 



Fig. 43. Row of cysts. 



Fig. 43, 44. Formation in and Iil)eration of zoospores 

 from cysts. 



Fig. 4J-47. Degeneration of cysts. 



