I'li'i 1 i)(;knv and Hi:i..\rioNfimi"s 



91 



AnuH'biiia is IkisoI primarily on tlu' nportiil simi- 

 larity hftwccn till' vi-_s{i'tiitivc mu-K'ar divisions in the 

 plasniodiuni and the (iroinitotic divisions in the liina.r 

 srronp of .tmoilui. Cook (^'28), as noted elsewhere, 

 held this similarity to he of ureat ])hyloiienetie sijr- 

 nitieanee and aeeordinijly helie\ed that the I'lasnio- 

 diophorales have oriicinated from the lohosoid amoe- 

 bae. Home (^'30) severely eritiei/ed Cook's view. 

 and after reviewing the variations of nuelear division 

 exhibited by the fungi, algae, and i>rotista. eon- 

 eluded that "the use of criteria relating to the type 

 of nuelear di\ ision is of very doubtful \alue at the 

 present time in diseussing the aetual relationshi)) be- 

 tween grou)) and group." 



The reported similarity of promitosis in certain 

 amoebae and the Plasmodiophorales has been fully 

 presented in Chapter 1 1 and need not be discussed 

 further at this point. Suffice it to repeat that Home, 

 Terby and Webb have refuted the rci)orts of pro- 

 mitosis in the Plasmodiophorales and described the 

 formation of well-defined chromosomes during the 

 vegetati\ e divisions. Furthermore, Miss Terby found 

 that the mieleole does not persist and divide into two 

 parts which are later ineorjiorated in the daughter 

 nuclei as the new nucleoli. Instead, the nucleole may 

 fragment and portions of it become stranded in the 

 cytoplasm between the nuclei, while the daughter 

 luicleoli are formed anew in the telo|)hases as in 

 higher i)Iants. There is accordingly no universal 

 agreement that jiromitosis, in the strict sense of 

 Xagler. occurs in the Plasmodiophorales. Xor is pro- 

 mitosis, in the modified sense of later workers re- 

 stricted to the lobosoid amoebae. Intranuclear divi- 

 sion with ill- or jjartly-defined chromosomes and 

 large persistent elongating, constricting, and divid- 

 ing nucleoli have been figured and described in spe- 

 cies of the Rhizomastigina. Thecamoebina, Coccidia. 

 Mvxosporidia, Englenoidina and .Siphonales. A simi- 

 lar persistence and behavior of the nucleole during 

 division has been recorded by N'emec (00). Mano 

 ('Oi), Wager {'01). I.undegardh ('12), and Tahara 

 ('1.5) for Alniis, Phaseolus, Solatium, Cucurbiia, and 

 Helianthiis, resi)ectively, where the process has been 

 referred to as ))seudoprotomitosis. On this basis, ac- 

 cording to Cook's line of argument, the Plasmodio- 

 phorales ;ire related in varying degrees to a large 

 number of .inim.il and plant families. Persistence 

 and division of the nucleole in the manner described 

 above, therefore, does not appear to be of much sig- 

 nificance, and as Doflein, Ti.schler ('22), Terby 

 ('24). Belar, and others have |)ointed out. it may be 

 found in various grou])s of organisms under certain 

 conditions. In light of these data it seems highly 

 doubtful that certain similarities in type of nuclear 

 division are an index of ])hylogenetic descent and 

 relationship. 



It is obvious from this discussion of ijhylogcny 

 and relationshij) that the Plasmodiophorales have 

 some develo))mental phases and cytological char- 

 acteristics in conmion with the Myeetozoa. Protozoa. 

 and jjolysporangiate s])ecies of the \\'oroninaceae. 

 Whet!ier this order has originated directly from such 



groups or de\el(>peil along |).'ir.illel lines with them 

 from a distant eonnuou ancestor, however, is still 

 UMt'crtain. Our kiunvledge of the critical stages in 

 the life cycle of the Plasmodio])horales as well as in 

 the groujis with which this order shows .-iftinity is too 

 incomplete to w.-irrant detinite conclusions at |)res- 

 ent. I'urther intensive study of these st.iges as wi'll 

 as the discovery of new sjiecics will (buibtless in- 

 validate many of the iiresent-day beliefs concerning 

 the Plasmodiophoraceae. Likewise the similarities 

 this family has in common with other groujis, which 

 now ])oint to definite lines of origin and relationshi|), 

 may in the future ))ro\e to be ])hylogenetically insig- 

 nificant. 



Xe\ ertheless. the Plasmodiophorales at jiresent 

 appear to be similar to JVoronlna pol i/ci/slis and the 

 biflagellate heteroeont species of the Proteoniyxa in 

 zoospore structure, and general type of development. 

 This similarity, of course, does not necessarily mean 

 a eonnuou origin and close relationship. It may 

 equally well be nothing more than ))arallelism in 

 development from se)iarate ancestors. This rela- 

 tionshi)) has. nonetheless, been emphasized rather 

 strongly in the discussions above, primarily with the 

 hope of encouraging intensive research along these 

 lines. 



\'ery little can be said at present about relation- 

 ships within the order itself, because the life cycles 

 of many species are not fully known. Furthermore 

 the genera are not sharply defined. As is indicated 

 in Cha))ter III, the relation and arrangement of the 

 resting spores is rather generally regarded as an 

 index of relationships and relative complexity. On 

 this basis Plasmodiophora has been regarded as the 

 most primitive genus, because its resting spores are 

 not united in cystosori. Tetrami/.ra, and Octomi/.ra, 

 with spores in tetrads .and oetads res])ectively, are 

 accordingly next in line. Sorosphaera and Sorodi.sciis 

 at present seem similar to these two genera in that 

 uninucleate spore mother cells or sporonts are de- 

 limited in wliich the meiotic divisions later occur. 

 Whether or not this is an index of relationship is, 

 however, questionable. Poli/mi/xa has the most ex- 

 tensive and complex zoosjiorangial stage of all 

 known genera, but its cystosori resemble those of 

 Lif/niera, a genus which Cook ('33) regarded as 

 primitive. 



BIBLIOCiHAPHV: I'HVLOOENY 



Abe, S. 19.33. Bot. and Zool. 1 : 1579. 



. 1934. Sci. Hept. Tiikyo-Hunrlca-Daifraku. .sec. R. 



1: 193. 

 AlexieflF, A. 1913. ,\roli. Protistk. -'9: 344. 

 Hessey, E. A. 193,5. A text-book of mycolofry. Philadelphia. 

 Cadman, Elsie .1. 1931. Trans. Hoy. Soe. Edinburfrh ~i~ : 93. 

 Calkins, c;. X. 1909. Pnitozooliifry. Pbiladelpliia. 

 . 1933. Hicilofry cif tin- |)r(itn/,i)a. .'iid, cd. Pliiliidel- 



phia. 

 Cavers, K. 191.5. New Phytol. 11: 30t. 

 Chattiin, E. 1910. ,\reli. /ool. Exp. et Gen. ."> ser. 5: ;?39, 



.'(i7. 

 Cienkowski. L. IHH.). Ark. .Mikro. Anat. 1 : -'03. 

 Clavlrv, D. M. 19;?9. Trans. IJrit. .Mveol. .Soe. 14: 227. 



