36 



PLASMODIOPHORALES 



the stages which Jones found in mosaic diseased 

 plants may relate to excitation and degeneration 

 products of the kind described by Kunkel, Goldstein, 

 Holmes. Sheffield, and others." At any rate P. tabaci 

 has but little in common with other known members 

 of genus, and the author agrees with Cook that 

 there is little if any justification at present for in- 

 cluding it in the Plasmodiophoraceae. 



Since he was able to produce mosaic-like symp- 

 toms in plants by inoculation with cultures, .Tones 

 believed his organism relates to the cause of tobacco 

 mosaic. Later in the same year, however, he. Link, 

 and Taliaferro ('2G) found that the organism could 

 be cultivated from healthy as well as diseased plants. 

 Furthermore, upon inoculation, mosaic-like symp- 

 toms appeared only when the amoebae and Plas- 

 modia came from diseased plants. They accordingly 

 concluded that P. tabaci is not the cause of mosaic 

 but may be a carrier of the causative agent. 



In 1937 .Tones retracted his previous views about 

 P. tabaci and redescribed it as the soil amoeba. Nae- 

 gleria gruberi, wliich he claimed is not an amoeba 

 proper but a stage in the life cycle of a myxomycete. 

 He excluded it from the Plasmodiophorales on the 

 grounds that: (1) several amoebae fuse and form a 

 large multinucleate plasmodium; (2) the nuclei di- 

 vide promitotically as in an amoeba; (3) the plasmo- 

 dium forms an aggregate of separate resting spores ; 

 and (i) it does not parasitize jilants. He furthermore 

 reported that N. gruberi may be an alternate host for 

 the mosaic producing organism in tobacco. .Tones' 

 above-cited reasons for excluding this organism from 

 Plasmodiophora are obviously no more critical than 

 those presented previously for including it in this 

 genus. The additional data which he has presented 

 do not clarify its taxonomic jiosition or relationsliip. 



P. SOLANI Brehmer and Biirner, 1930. Arb. Biol. Reich- 

 sanst. f. Land-u. Forstwirtsch. 18: 1-S4, pi. 1, fifr. 1-32. 



Brehmer and Earner gave this name to an oval. 

 4.3.5-.5..5 /i X 2.9 fi, amorphous, pale yellowish-green 

 organism with a distinct refringent sheath which 

 they found in older portions and parenchymatous tis- 

 sues of potato stems sliowing leaf roll, mosaic, and 

 other degenerative symptoms. The thallus divides 

 into as many as eight daughter cells, and tliese in 

 turn give rise to vesicles or spores which are subse- 

 quently liberated by the breakdown of the daughter 

 cells. The spores produce a filamentous zoospore, 5 jx 

 in length and a fraction of a micron in diameter. 

 Brehmer and Barner found all of these stages in fil- 

 tered juices of diseased plants as well as in plants to 

 which virus symptoms had been communicated by 

 grafting and concluded tlierefrom that P. Solaiii is 

 the cause of potato virus. These authors pointed out 

 the similarities of tlieir organism to .Tones' parasite 

 Calkinsi and the so-called "X" bodies of various in- 



1 Kunkel, L. O. 1921. Hawaiian Sugar Planters' Assoc. 

 Bot. Ser. 3: 108. 



Goldstein. B. 192T. Bull. Torrev Bot. Club 54: 285. 



Holmes. F. O. 1938. Bot. Gaz. 86: 50. 



Sheffield, F. M. I>. 1931. Ann. Appl. Biol. 18: 471. 



vestigators and considered it to be either an inde- 

 pendent amoeboid entity capable of spore formation 

 or a Plasmodium living in symbiotic relationshi)) 

 with the plastids. They regarded it as a member of a 

 hitherto unknown group of the Archimycetes allied 

 to the Plasmodiophoraceae. It has subsequently been 

 reported by Moesz ('38) on potatoes in Hungary. 



There is little in the life cycle of this organism, as 

 described by Brehmer and Barner, which indicates 

 relationship to Plasmodiophora, and it is accordingly 

 excluded from the genus. 



P. THEAE Fitzpatrick, 1930. The lower fungi-Phycomy- 

 cetes. New York. 



See Sorosphaera Theae Speschnew. 



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