20 



PLASMODIOPHORALES 



the products of gametic union or incomplete cleav- 

 age. Tetraflagellate zoospores were likewise found 

 bv Couch et al. in Octomi/j-a, but no fusions were ob- 

 served. However, in this genus as well as in Mem- 

 hranosorus Whitten and ^^'ernham each reported re- 

 duction at sporogenesis. which presupposes karyog- 

 amy at some state of development. Miss Whilfen be- 

 lieved that karyogamy occurs during the akaryote 

 stage of O. Achli/ae. 



It is obvious from this review that the data on sex- 

 uality in the Plasmodiophorales are quite limited. In 

 S. stibierranea, tlie only species in which gametic 

 fusion has actually been observed, the respective 

 gametes are reported to be alike and show no struc- 

 tural, mobile, and physiological differences. In this 

 species at least sexual reproduction appears to be 

 isogamous. Whether it is homo- or heterothallic is 

 not known, since no studies involving monospore cul- 

 tures have yet been made. Therefore, any discussion 

 at present of sex determination, haplosynoecism, 

 haploheteroecism, antithetic alternation of gameto- 

 and sporophytic generations, etc., in the Plasmodio- 

 phorales must be speculative and, in light of the 

 meager present-day knowledge, largely futile. 



bibliography: cytology and se.xiality 



Alexieff, A. 1913. Arch. Protistk. 39: 344. 



Belar, K. 1936. Ergeb. Foitschr. Zool. 6: 335. 



Blomficld, ,T. E., and E. J. Schwartz. 1910. Ann. Bot. 34: 



3.5. 

 Calkins, G. X. 1933. Blolojry of the protozoa. Philadelphia. 

 Chatton, E. 1910. Arcli. zool. Exp. 5 ser. 5: 339, 36T. 

 Cook, W. R. I. 1936. Trans. Brit. Mycol. Soc. 11: 196. 



. 1938a. New Phytol. 37: 330, 398. 



• . 1938b. Ann. Bot. 43: 347. 



. 1931. Ann. .Mycol. 39: 331. 



. 1933. Arch. Proti.stk. SO: 179. 



, and E. J. Schwartz. 1939. Ann. Bot. 43: 81. 



, and . 1930. Philos. Trans. Roy. Soc. London 



318 B: 383. 

 Couch, J. X., J. Leitner, and A. Whiffen. 1939. Jour. Elisha 



Mitchell Sci. Soc. 55: 399. 

 Doflein, E. 1916. Lehrbuch der Protozoenkunde 4th ed. 



Jena. 

 Favorsky, W. 1910. Mem. Soc. Nat. Kieff 30: 149. 

 Ferdinandsen, E., and O. Winge. 1930. Ann. Bot. 34: 467. 



Fedorintschik, N. S. 1935. Summ. Sci. wk. Inst. pi. protect. 

 Leningrad 1935:69. 



Harper, R. A. 1900. Bot. Gaz. 30: 317. 



. 1914. .\mer. Jour. Bot. 1: 137. 



Home, A. S. 1911. Rept. Brit. Assoc. Adv. Sci., Ports- 

 mouth, p. 573. 



. 1930. Ann. Bot. 44: 199. 



Jahn, E. 1907. Ber. Deut. Bot. Gesell. 35: 23. 1908, Ibid. 

 36a : 343. 



Jones, P. M. 1938. Arch. Protistk. 63: 313. 



Kninzlin, H. 1907. Ibid. 9: 170. 



Ledingham, G. A. 1939. Canad. Jour. Res. C, 17: 38. 



Levine, I., and M. Levine. 1933. Jour. Cancer Res. 7: 163, 

 171. 



Lutman, B. F. 1913. Vermont Agr. Exp. Sta. Bull. 175. 



Maire, R., and A. Tison. 1909. Ann. Mycol. 7: 22%. 



, and . 1910. Bull. Soc. I.inn. Normandie 6 ser. 



3:57. 

 , and 



-. 1911. Ann. Mycol. 9:336. 



Milovidov, P. F. 1931. Arch. Protistk. 73: 1. 



. 1933. C. R. Soc. Biol. 109: 170. 



. 1933. Arch. Protistk. 81 : 138. 



Niigler, K. 1909. //)W. 15: 1. 



Nawaschin, S. 1899. Flora 86: 404. 



. 1901. Kiev Lap. Ohsch. Jest. 17: 1: XXXVI. 



. 1934. C. R. Acad. Sci. Russie 1934: 173. 



N'emcc, B. 1911. Bull. Inter. Empr. Fran. Joseph Acad. Sci. 

 16: 69. 1913, /hi'rf. 18: 18. 



Olive, E. W. 1907a. Trans. Wise. Acad. Sci., Arts and Let- 

 ters 15:7,53. 



. 1907b. Sci. n. s. 35: 366. 



0.sborn, T. G. B. 1911a. Rept. Brit. A.s.sn. .\dv. Sci. Ports- 

 mouth, p. 573. 



. 191 lb. Ann. Bot. 35: 371, 337. 



Palm, B. T.. and M. Burk. 1933. Arch. Protistk. 79: 363. 



Pavillard, J. 1910. Prog. Rei. Bot. 3: 475. 



Prowazek, S. 1903. Osterr. Bot. Zeitschr. 53: 313. 



. 1905. Arb. Kais. Gesundheit 2-2: 396. 



Schwartz, E. J. 1910. Ann. Bot. 34: 511. 



Skupien-ski, F. X. 1918. C. R. Acad. Sci. Paris 167: 960. 



Terby, J. 1933. Mem. Roy. Acad. Belg. 7: 1. 



'—. 1934. Bull. Roy. Acad. Belg. 5 ser. 10: 519. 



. 1933. Mem. Roy. Acad. Belg. 11: 1. 



Webb, P. C. R. 1935. Ann. Bot. 49: 41. 



Wenyon, C. M. 1936. Protozoology 1 : 66. 



Wernham, C. C. 1935. .Mycologia 37: 363. 



Whiffen, Alma. 1939. Jour. Elisha Mitchell Sci. Soc. 55: 343. 



Winge, (). 1913. Ark. f. Bot. 13, no. 9: 1. 



Wissenlingh, C. 1898. Jabrb. Wiss. Bot. 31: 619. 



Vendo, V., and K. Takase. 1933. Bull. Sericult and Silk 

 Inc. Japan 4, no. 3: 4. 



Chapter IV 



Classification and Description of Species 



The Plasmodiophorales include one family, Plas- 

 modioplioraceae, and approximately eight genera 

 and twenty-three species. Numerous other genera 

 and sjiecies have been added at various times, but 

 these liave either been merged with existing genera 

 or excluded entirely as invalid. A natural classifica- 

 tion is well nigh inijjossible at present because so lit- 

 tle is known about tiie critical diagnostic characters 

 of most siJCcies. Furtliermore, the genera are not 

 shar])ly defined and, as Palm and Burke ('33) have so 



well em])hasized, tend to merge and overlap, so that 

 in certain members generic distinctions are difficult 

 to recognize. The oldest and most frequently used 

 criterion of classification is the grouping assumed 

 by the resting spores at maturity. This criterion was 

 introduced by Schroeter in 1 897, who separated the 

 genera on the basis of whether the spores are free or 

 united in clusters and cystosori. Schroeter also em- 

 ])Iiasized the presence or absence of a soral mem- 

 lirane as a distinctive character of Tetrami/.ra and 



