POLYMYXA 



G3 



oomiiK'tcIy tilliiii; tin- host cell. ZoDspiiriiiisiia ;m(] 

 zoospores unknown. 



I';ir;isitii' in tlic Ic.iMs and roots of Isoftts lacii-i- 

 tris in Swi'ilin (^I'alni. l.o. ) and Ni'W .Icrsi-y. U.S.A. 

 (Karling. "Si), (■.•luslns; larjrf. dark spots in tin- iiost 

 tissuo but no hypcrtropliy. 



This spi'firs is so littK- known at jnxscnt that its 

 identity is very doulitful. As Cook pointed out, it may 

 well he identieal to L. Jiinci, but some of the rest- 

 injl si)ore elusters tifiured by Palm are strikini;ly 

 like those of speeies of Soroxphncra and Mrriihraiid- 

 soru.i. The jiresent writer's observations on this s))e- 

 cies in 1931- were very limited, and sinee then he has 

 not added any further data on its structure ,ind de- 

 velopment. 



L. VASCULARUM (Matz) M. T. Cook (\'9) does not 

 appear to In- a valid species. See PlimmndUtjihom vtm- 

 ritUivum. 



.\DDiTiox.AL bibliography: Lic/iiicm 



Cook, \V. H. J. 19.'(>. Trans. Brit. Myool. Soc. 11 ; 19(>. 19.^, 



I hill. 12: 2SJ. 



. 19iSa. lUiU. Soi-. Mycol. France U: 1().>. 



. 19.'81>. Ann. Hot. i2: 347. 



-. 19:}-'a. Hoiijr Koiifr Nat. Suppl. No. 1 : 2i). 



. 19:l.'l). .lour. Dei)t. .\pr. Porto Rico 1(>: +09. 



, 19:«. tllaniorau County Hist. Nat. Hist. 1: ;.'13. 



. 19:U. Watson's .Microscope Record — : 'i, 9. 



Guyot, .\. I.. 19.'7. Rev. path. Ent. Afrr. It: 17(>. 

 Hiidehrand, A. A. 19;U. Canadian .lour. Res. 11: 2i. 

 KarlinfT, .T. S. 1934. Torreya 34: 13. 



Palm, H. T., and .M. Hurk". 1933. Arcli. Protistk 79: 363, 

 Smith, .\. I.., and .1. Ranisliottom. 1917. Trans. Brit. Mycol. 



Soc. (>: -'31. 



POLYMYXA 



Lcdinglmm, llKiS, Phvtopath, 23: 20. 



(I'LATF. 12, FICS. 1-22) 



Cvstosori or restinjj spore clusters indefinite in 

 size and .shajjc, without a common membrane ; formed 

 by cleavage of a naked multinucleate plasinodium. 

 Resting spores few or numerous, variable in shape, 

 Zoos)>orangia conjoined in a more or less linear 

 series : formed by tin- se))t.ition of an elongate, lobed, 

 irregul.-ir and tubular thallus, which may extend 

 through one or more host cells: exit tubes one or 

 more, variable in length, and septate. Zoospores from 

 resting spores and zoosporangia biflagellate and 

 heterocont. 



Poliimjisa is a monotypic genus, and like Sponc/o- 

 spora, Lifiiiirra, Plasmodiophora, etc., includes zoo- 

 sporangial and naked ))lasni<)dial stages in its life 

 cycle. The zoos))ores a))parently jienetrate the host 

 cell wall directly (fig. (i, 7) aiul lie in the host ])roto- 

 plasm as small globose bodies. As is shown in figure 

 8, they soon begin to increase in size and elongate, 

 and as growth continues they become lobed (fig. 9, 

 10), branched, irregular, and tubular, and sometimes 

 extend through the host walls into adj.icent cells. In 



this manner l.irgi- septate thalli .are deM-loped which 

 ;ire couipletely surrounded from the begiiniiug by ;i 

 thin hyaline w.ill .lud closely resend)lc the thalli of 

 Srplol pidiiim, I.nifcniiliiim, M iizociji'ium, etc. The 

 segments of the th.alli beeonu' zoosjMjrangia (fig. 1 1 ) 

 .-iiul dcvcloj) one or more septate exit tubes of vari- 

 able length. The protopl;ism then undergoes cleav- 

 ;ige into zoosjiores which exhibit considerable move- 

 ment within the /.oospor.angia before emerging. 

 When mature, they emerge fully formed in succes- 

 si(Ui from the exit tubes, become amoeboid for a few 

 nu)uients, and swim away. 



The zoospores are ))yriform and ov.ite in slia))e, 

 usually uninucleate, and ])Ossess a long and short 

 flagellum attached to the nucleus near the anterior 

 end of the spore body (fig. 1-t). A few binuclcate 

 zoospores with four flagella have been found, but 

 I.edinghain v\'as not certain whether they were the 

 result of unequal cleavage or fusion of two biflagel- 

 late s))ores. During active swimming the flagella may 

 extend out in front, but the zoospores are usually 

 propelled from behind, according to Ledinghani. 

 They rotate on their axes or roll over in swimming, 

 and their motility appears to be somewhat slower 

 than that of most chytrid zoospores. After an active 

 swimming stage of about two to three hours, the 

 flagella disappear, and the zoospores become amoe- 

 boid again (fig. o). In this state they move about by 

 pseudopodia, and may often engulf small food par- 

 ticles or objects. These amoeboid zoosjiores may 

 penetrate and reinfect host cells, but it is not certain 

 from Ledingham's account whether tliey give rise to 

 another crop of zoosjiorangia or develop into large 

 multiinicleate plasmodia. A))parently they ]iossess 

 both ))otentialities. 



The thallus from which the resting sjiore cluster 

 is formed begins in the host cell as a naked uninu- 

 cleate amoeba (fig. 12), and at no time does it jiossess 

 a membrane or wall. As it increases in size, repeated 

 nuclear divisions occur, and a multinucleate Plas- 

 modium is soon formed. Its shajjc changes constantly 

 as it moves about in the host cell. It may frequently 

 be long and tenuous, extending the full length of the 

 host cell, or form a crescentric mass around the host 

 nucleus with long thread-like, r.idiating pseudo])odia. 

 These pseudo))odia are later retracted as the jjroto- 

 ))lasin becomes denser, and the plasmodium may then 

 segment into a number of portions or meronts (fig. 

 18) which often lie in rows or closely ))aeked grou))s 

 in the tr.ichcal and cortical cells. Occasionally fusion 

 of several separate ))l.asuu)dia may occur in the same 

 host cell (fig. II-). but I.edingham was not certain 

 whether these were th.alli of ojiposite sex or merely 

 meronts derived by division of a common schizont. 

 He was unable to count the chromosomes in the nu- 

 clear divisions preceding resting s))ore formation 

 and accordingly found no evidence of meiosis at this 

 stage. 



In the early stages of growth the ))lasuu>dium is 

 very vacuolate, but as devcloiiment |)roceeds the 

 vacuoles decrease in size. As a result the thallus be- 

 comes more granular and refringent in texture and 



