DOlDTFn, (iKNEHA 



Slovakia (Xcnicc, I.e.). tlie U. S. .\. (Rawliiigs. '25), 

 and France ( .') (Cuyot. '27) witliout (•.nisiiiK liyper- 

 trojiliy of tlie invaded tissues. 



Si>rolpitliinii liftar lias lieen tlie sulijeet of eon- 

 siderable diseussion sinee tlie time of its discovery liy 

 N'eniee. He described it as a species of the Cliytri- 

 diaccae with close iirtiiiities with tlie l'lasniodi(i])lio- 

 raceae, hut hecause of the jircsenee of lar«e. tliiii- 

 walled 7.oosi)oraiigia he did not l)elie\ e it siiould he 

 included in this family. Since similar zoosjiorangia 

 have subsequently been found in several genera of 

 the l*l;isniodiophoraceae. this obji-etion is no longer 

 significant. The large, thick-walled, stell.-ite resting 

 cysts surrounded by a thin envelope which Neniec 

 figured are now generally recognized as relating to 

 Olpidium, and outside of these cysts there is nothing 

 in the life cycle of Sorolpidium, as described by 

 Nemec. which excludes it from the Plasmodiopho- 

 raceae. The presence of large holocarpie zoospo- 

 rangia and multinucleate resting spores which pro- 

 duce several zoospores is in line with more recent 

 discoveries in other genera of this family. Saccardo 

 ('26) likewise included .S'. Brtae among the Chytri- 

 diales. Winge ('13), however, asserted that it is 

 closely related to Pi/rrho.soriis and the Plasmodio- 

 phorficeae. Subsequent workers, on the other hand, 

 have questioned the identity of Sorolpidium as a dis- 

 tinct genus of this family and contended that it re- 

 lates to Lif/niera. Cook ('2(3) regarded it as a combi- 

 nation of Lif/niera and Asteroci/sii.s, a view which 

 Giiyot sui)])orted in 1927. The latter worker suc- 

 ceeded in inoculating roots of Beta vulgaris with L. 

 verrucosa and Asteroci/stis radicis, and concluded 

 that Nemec's fungus is merely an accidental associa- 

 tion of these two species in the same host tissues. 

 Cook ("32, '33) later incorporated Sorolpidium in 

 Lif/niera and classed S. Betae (pro parte) as a syn- 

 onym of L. J unci. In the sha])e of its cystosori and 

 the fact that it docs not cause hypertrophy of the 

 host tissues .V. Betae is very similar to species of 

 Lif/niera. Should it prove to be a species of this genus 

 its identity to L. Junci and L. verrucosa will none- 

 theless remain somewhat questionable, because 

 Nemec unfortunately did not give any measurements 

 of the sjjorangia and zoospores. 



The life cycle of .S'. Betae is similar to that of other 

 ])lasmodio])horaceous si)ecies. The earliest recogniz- 

 able stage consists of a uninucleate oval or spherical. 

 highly vacuolate thallus (fig. 1) which us\ially lies in 

 the primordial utricle of the host cell. This thallus is 

 probably the result of zoospore infection, although 

 Nemec was uncertain whether the zoos|)ore enter di- 

 rectly or first become amoeboid. Within the host the 

 thallus grows in size (fig. 2. 3. K and 5), becomes 

 multinucleate and i)lasmodium-like. The division of 

 the nuclei (fig. 3) during this developmental phase 

 appears to be "promitotie,"' according to Nemec's 

 figures, and no sharply-defined chromosomes are 

 formed. One or more plasmodia (fig. I. o) may occur 

 within a single host cell and are usually embedded in 



' Cook {'J>i) stated that N'eniee did not figure "promito- 

 sis," but he obviously overlooked figure 3. 



the host ))rotopIasm or occupy Ihc icntrjil vacuole. 

 They may be spherical. o\al, clongati', or take the 

 shape of the cell which they occupy. Sometimes, the 

 ))lasmodium may form .i broad band or ))latc around 

 the vacuole (fig. 5). 



.\t maturity the ))lasuu)(iiuui develops .i rrlati\ely 

 thin, enveloping nienibranc and may be transformed 

 directly into a /.oos|)orangiuni. In tiiis respect Sorol- 

 pidium differs from I'lasmodiophora, Lii/iiiera, and 

 Octom/ixa, where the plasmodium is reported to 

 cleave into a number of uninucleate segments which 

 develop into zoosjiorangia. This difference suggests 

 perliaps that the zoosjiorangia (fig. (i, 7) which 

 Nemec described may relate to a species of Olpidium 

 (.isteroci/stis) with large stell.ite resting sjjores. It 

 is to be noted in this connection, however, that the 

 sporangia of Olpidium usually form more or less 

 elongate exit tubes, which are lacking in Nemec's 

 ■S'. Betae. On the other hand, Nemec may have over- 

 looked the cleavage stage of the plasmodium which 

 results in the formation of several zoos))orangia. His 

 text-figure .5 suggests this possibility. At any rate, 

 the protoplasm of the zoos))orangium cleaves into un- 

 inucleate segments (fig. 6, 7) which become zoo- 

 spores and emerge through an irregular opening in 

 the sporangium wall. The zoospores from such spo- 

 rangia are usually uninucleate, oval or pyriform 

 (fig. 8) and unifiagellate {?). Unfortunately Nemec 

 did not say whether they were anteriorly or pos- 

 teriorly flagellate, which would have settled conclu- 

 sively their identity as well as that of the large zoo- 

 sporangia shown in figures 6 and 7. If these zoo- 

 spores relate to a plasmodiophoraceous sjiecies they 

 will doubtless prove to be anteriorly bifiagcllate and 

 heteroeont. 



In other mature plasmodia which occur in almost 

 emjity host cells. Nemec found that the nuclei lacked 

 nucleoli and were comparatively jjoor in chromatic 

 material (fig. 9). Peripheral chromosomes later ap- 

 peared (fig. 10). and the nuclei divided in regular 

 mitotic fashion (fig. 11-15). The appearance of 

 these nuclei and their manner of division are very 

 similar to what has been described in most of the 

 other genera, and suggests that figures 9 to 1.5 relate 

 to the so-called "akaryote" stage and ])ro))hases of 

 meiosis preceding sporogcnesis. Some of the nuclei 

 in figure 10 have six chromosomes. The same num- 

 bers are present in figures 11 and 15. but whether or 

 not this is the basic number in Sorolpidium is uncer- 

 tain. Nemec described a second mitosis in such plas- 

 modia in which the chromosomes are larger, elongate, 

 and rod-shalied. but it is difficult to reconcile his con- 

 clusions about this division with ))revious and subse- 

 quent descri])tions of the hoineoty|)ic mitosis in other 

 genera. 



These jilasmodia. nonetheless, devcloji a thin en- 

 veloping membrane and cleave into uninucleate seg- 

 ments (fig. 16), which form fairly thick walls and 

 become resting spores. The envelo))ing membrane 

 soon disappears, but the resting s|)ores remain at- 

 tached and thus form cystosori of various sizes and 

 shapes (fig. 17-21). They may consist of a linear 



