KXCI.rnKD OEXKUA 



77 



niiiio wlu'tlu-r or not tlic divisions riscinlilo tlu- pro- 

 mitosis (Itscriluii for otlifr <iinir;i. 



Sovcral ;iiiio(l);u- and small plasinodia may co.i- 

 l«'si-i- and form larjtcr plasmodia. accordinf; to Elliott, 

 which migratf dcfpcr into the infected tissue (fig. 

 3i) in much the same manner described l\v Kunkel 

 for Spoiif/ospora. I.arjie plasmodia may contain from 

 200 to 300 nuclei, and at maturity form l.irjie multi- 

 nucleate cysts (fifi. 37-1-2). Klliott reported that 

 eaeli ))l.ism(idium forms a single cyst, hut liis liirures 

 sutrjiest that more than one may be j)roduccd. The 

 plasmodimn fills the host cell at maturity (fig. 36- 

 38). becomes more dense in the center, condenses, 

 and eventually forms a tliick. smooth wall (fig. 

 39-H). .\fter a short rest period the cyst germi- 

 nates, and in this process the wall becomes very thin 

 (fig. 13. H). and the protoplasm cleaves into nu- 

 merous zoospores. In this manner several genera- 

 tions of zoospores per season are formed in infected 

 roots and pox lesions, each generation of which mi- 

 grates deeper into the tissues. Eventually "all plas- 

 modia seem to collect, cease advancing, turn back- 

 wards, and leave the pit for the soil," according to 

 Tabenhaus. These plasmodia are believed to encyst 

 in the soil and live through the winter in this stage. 



Soil rot. Jiit. or ))ox is a widely distributed and 

 common disease and has been reported from a num- 

 ber of states (Halsted, '90, '92, '96; Price. '9.5; 

 Duggar, '97; Townsend, '99; Wilcox, '06; Barre, 

 '10; Tabenhaus, '14, '16; Harter, '16; Poole, '22, 

 '24, '2.5; Anonymous. '21', 26; Harter and Weimer, 

 '29, and others). Pox may also occur on the white 

 potato, turnips, and possibly beets and tomatoes 

 (Tabenhaus. '18). The cause of pox. however, has 

 been the subject of much controversy. Halsted at- 

 tributed it to a filamentous fungus which he named 

 Acroci/stis batatas, but from extensive study of the 

 disease. Tabenhaus ('14) and Elliott concluded that 

 A. batatas is non-existent and had ])reviously been 

 mistaken for anotlier organism. The latter worker 

 claimed that pox is caused by a myxomycetous fun- 

 gus which he named C. batata. Elliott further as- 

 serted that Halsted had figured several stages of this 

 slime mold, and he accordingly listed Acroci/stis 

 batatas as synonymous with C. batata. Tabenhaus 

 ('18) confirmed Elliott's observations in Texas, and 

 found that another fungus. .4ctiiwmi/ces poolensis, 

 may also occur as a suiJcrfieial wound ])arasite in pox 

 spots produced bv ('. batata. 



Since that time the existence of cysts and other 

 stages of C. batata has been seriously questioned and 

 denied by Manns and Adam. In mature pox lesions 

 no evidence of an organism resembling a slime mold 

 was found by these workers, and they (21) inter- 

 jireted the so-called cysts of Elliott as "i)roducts of 

 metabolism in the form of reserve substances." Later 

 Manns ('24) demounted some of the pox material 

 which Elliott had stained with Flemming's triple dye 

 and restained it with Ziehl's earbol fuchsin. and in 



each instance he found ."in .Icl'nioin i/crs s|)ccies pres- 

 ent. He ('2.5. '2(i) and .\d;ims (2!)) l;iter questioned 

 the existence of ('. batata and m.-uutained that pox 

 of sweet potato is caused by a s))ceies of Actino- 

 myces. Harter and Weimer ('29) were also unable 

 to isolate ('. batata from ))ox lesions or find any evi- 

 dence of zoospores. ))l.isniodi.a and cysts in fixed and 

 stained ))repar;itions. 



This is the |)resent st;itus of ('. haltifa in relation 

 to l)ox. Elliott and Tai)enli;nis douiitless iiail some 

 sal)roi)hytie plasmodial organism .-it hand, but 

 whether or not it is a species of the Plasmodiopho- 

 rales is obviously questionable. Fitzjiatriek and Cook 

 excluded it from this order, but Saccardo ("31 ) listed 

 it among the valid siiecics. Palm and Hurk. however, 

 implied that it is valid but stands distinctly ajjart 

 from the other genera because of its method of cyst 

 formation. Except for the presence of zoospores, 

 ('. batata is somewhat similar to Leptomi/xa rctice- 

 lata var. hum'di, a saprophytic proteomyxean organ- 

 ism which Miss McLennan ('31) found in hops. 

 There are a large luimber of saprophytic, soil in- 

 habiting organisms of this tyjie which may become 

 secondary invaders of roots, and unless they are 

 earefulh^ studied and cultured they may be readily 

 mistaken for stages in the life cycle of plasmodio- 

 I)lioraecous species. 



bibliography: E-XCLFded genera 



Adams, J. F. 19-'9. Phytopath. 19: 179. 



Anony. U)-'4. U. S. Dept. Agr. PI. Dis. Rept. .Siippl. 34. 



19Jti, Ibid. 45. 

 liarre, W. H. 1910. South Carolina Exp. Sta. J3 .\iin. Rejit., 



p. .'3. 

 Cook, W. R. I. 1933. Arch. Prntistk. 80: 1T9. 

 Dupfrar, ,1. F. 1897. U. S. Dept. Apr. Farm. Hull. 2G. 

 Elliott, ,1. A. 1916. Sci. n. s. 44: 709. 

 Fitzpatrick, H. M. 1930. The lower fungi — Phycomycetes. 



New York. 

 HaLsted, B. D. 1890. New .Tersey Agr. Exp. .Sta. Bull. 76. 

 . 189:2. Xew Jersey Agr. Exp. Sta. IJth Ann. Rept, 



p. 2m. 1896, Ibid. 17tli .\nn. Rept. p. 39. 

 Harter, L. L. 1916. V. S. Dept. Agr. Farm. Bull. 714. 

 , and J. L. Weimer. 19J9. U. S. Dept. Agr. Tech, 



Bull. 99. 

 .\Iaire, R., and .\. Tison. 1909. ,\nn. Mycol. 7: -226. 

 Manns, T. F., and .1. F. Adams. 1921. Delaware .\gr. Exp. 



Sta. Bull. 139: 18. 19J-', Ibid. 133: 36. 1934, Ibid. 135: 



25. 1935a, Ibid. 139: 34. 1935b, Ibid. 141: 24. 1936, Ibid. 



147: 39. 

 McLennan, E. I. 1931. Australian Journ. Exp. Biol. 8: 9. 

 Palm, B. T., and M. Burk. 1933. Arch. Protistk. 79: 371. 

 Poole, R. F. 1933. New .Jersey .\gr. Exp. Sta. Bull. 356. 



. 1934. New .lersey .\gr. 6: 16. 



. 193.5. Phytopath. 15: 3H7. 



Price, R. H. 1895. Texas Agr. Exp. Sta. Bull. 36: 309. 

 Prowazek, S. 1905. .\rh. Kais. C.esuiidhelt 22: 396. 

 Rietschel, P. 19.36. Arch. Protistk. 86: .349. 

 .Saccardo, P. .\. 1931. Sylloge fuMgoriiiii 25: 16. 

 Tabenhaus, .T. .1. 1918. .Jour. Agr. Res. 13: 437. 

 'Jownseud. C. O. 1899. .Maryland Agr. Ex|). Sta. Bull. 60. 

 Wilcox, E. M. 1906. Alabama Agr, K\|i. Sta. Bull. 135. 



