66 



PLASMODIOPHORALES 



ear rows of sporangia. Large single zoosporangia 

 spherical, oval and elongate, produeing up to 21' zoo- 

 spores ; zoosporangia in sporangiosorus usually 

 small, spherical and ovoid. 5-6 /x in diameter with 

 thin, hyaline, smooth walls and a short exit pupilla; 

 forming usually 1—2 zoospores which emerge fully 

 formed and swim direeth' away. Zoospores pyriform, 

 egg-shaped and small; flagellum 10—1.5 /x. Cystosori 

 ( .'') of indefinite size and shape, 20—60 /x, in diameter. 

 Resting spores oval and spherical, 8 /x; germination 

 unknown. 



Parasitic in the cortical cells of young roots and in 

 root hairs of Agrostis alba, Aira Cupaniana, Briza 

 viaxlma. Poa annua, Setaria glomerafa, Stellaria 

 media, Silene coloraia, Capsella bursa pastoris, Bis- 

 cutella lyrata. Delphinium longipes, Lotus ornitho- 

 podioides, Medicago tribuloides, Trifolium resupina- 

 tum, .Inagallis ari'ensis, Borrago officinalis, Dinaria 

 reftejca, Barisia Trijcago, hamium amplexicaule, 

 Fedia cornucopiae. Campanula dichoioma, Calen- 

 dula arvensis, and Erigeron canadensis in Italy 

 (Borzi, I.e.) ; Triglochin palustre, Juncus Gerardi 

 and Ranunculus sceleratus in Germany (Fischer, 

 '92) ; in numerous species of grasses in Belgium (De 

 Wildeman, '93) ; and Stellaria media in the U.S.A. 

 (Barrett, '35), without causing hypertrophy of the 

 host cells. 



The above diagnoses differ somewhat from those 

 given by Borzi. since it is now generally agreed that 

 the antheridia and oogonia which he described relate 

 to another organism. The plasmodia (fig. 26), spo- 

 rangiosori, (fig. 27, 28) and zoospores (fig. 23, 36), 

 however, doubtless relate to a species of the Plas- 

 modiophoraceae. The identity and relationship of R. 

 hypogeae have been the subject of lengthy discussion 

 and speculation since the time of its discovery in 

 ISS-t. Borzi was uncertain of its taxonomic position, 

 but in 1892 Fischer pointed out that it is probably a 

 combination of two or more fungi, Olpidium- and 

 Oipidiop.iis-\ike species and a Jf'oronina-like fungus. 

 Because of the ])resence of sporangiosori and cyto- 

 sori, he placed it next to IVoronina in the Syncliy- 

 triaceae. A year later de Wildeman found it in the 

 roots of various grasses in Belgium and from a study 

 of the plasmodia and sporangiosori came to the same 

 conclusions as Fischer concerning its identity and re- 

 lationship. Schroeter ('97), however, emphasized 

 the heterogamous type of sexual reproduction de- 

 scribed by Borzi and included 7?. hypogeae in the 

 I.agenidiaceae. In 1911 INIaire and Tison pointed out 

 the similarities between certain of its stages and 

 those of their new genus Ligniera, and suggested that 

 R. hypogeae is ])robably a combination of L. verru- 

 cosa and another fungus. This viewpoint was sub- 

 sequently supported by Guyot ('27), and Cook ('33). 

 Minden (11) excluded the sexual phase as relating 

 probably to a species of Myzocytium, included the 

 remaining stages of Borzi's fungus in the Synchy- 

 triaceae, and pointed out that it is very similar to 

 Worouina except for its anteriorly iniiHagellate zoo- 

 sjiores. Fitzpatrick ('30) believed that the large zoo- 

 sporangia relate to Olpidium. In more recent years 



Barrett has thrown further light on the identity of 

 Borzi's fungus. He found a species of Ligniera in 

 roots of Stellaria media which was frequently asso- 

 ciated with antheridia, oogonia and oospores of the 

 type described by Borzi. The zoosporangia of what 

 he called Ligniera sp., are comparatively large and 

 isolated with fairly broad exit tubes and form ante- 

 riorly biflagellate zoospores as in Plasmodiophora, 

 Polymyxa, Octomy.ra, etc. Antheridia and oogonia 

 may occur in association with Ligniera or are iso- 

 lated in separate roots, and Barrett thus concluded 

 that the two are unrelated. In his opinion Borzi's 

 fungus is a combination of Ligniera and a species of 

 the Lagenidiales ( Ancylistales). Barrett's observa- 

 tion is particularly noteworthy in that it is the first 

 record of biflagellate zoospores in the genus Lig- 

 niera. The early suggestion of Maire and Tison that 

 R. hypogeae is in part a species of Ligniera thus ap- 

 pears to be confirmed by the observations of Barrett. 

 It is further supported by the fact that this fungus 

 does not cause hypertrophy of its host cells and oc- 

 curs in some of the hosts which harbor other species 

 of this genus. Whether or not it is identical to L. 

 iwrrucosa as Maire and Tison, and Cook suggest, 

 however, is not certain at present, since well-defined 

 cystosori and resting spores have not yet been de- 

 scribed. 



SOROLPIDIUM 



Xemec, 1911. Ber. Dcut. Bot. Gcs. 29: -18. 1911b, 

 Bull. Int. Enip. Fran. Joseph Acad. Sci. 

 16: 69. 



(plate 13, FIG. 1-25) 



Cystosori one or more in a cell, indefinite in size 

 and shape; flat and almost round, oval, elongate, 

 angular and lamellate ; consisting of few to many 

 resting spores arranged in linear series, in single or 

 double, flattened layers, or irregular masses. Resting 

 spores variable in size and shape, usually polygonal 

 or hexagonal at first but becoming knobby and some- 

 what stellate at maturity ; usually producing several 

 zoospores in germination. Plasmodia one to several 

 in a cell, variable in size and shajie, often lying in 

 the central vacuole or surrounding the latter as a 

 broad band or plate ; ])roducing either zoosporangia 

 or cystosori ; schizogony unknown. Zoosporangia one 

 or more in a cell, spherical, oval, and elongate ; pro- 

 ducing few to many zoospores which emerge through 

 an irregular opening in the sporangium wall. Zoo- 

 spores oval, obpyriform, uniflagellate (.''), size un- 

 known. 



S. BETAE Nemec, I.e., pi. 1, 2, text-figures 1-6. Ibid. 

 lH:-2i. 



Resting spores 1.2X5 fi- — 1.6X'5-2 fi. For further 

 details see the generic diagnosis above. 



Parasitic in the roots of Beta vulgaris^ in Czecho- 



• Cook (";36) reported that Xemee found the parasite in 

 B. mnritimri, which is obviously a mistake. 



