SOUOSIMIAKHA 



41 



SOROSPHAERA 



Solirocter, .1. 1S()(>. Colm's Kivpt. Fl. von Sililo- 

 sicns .■{ : l."{."). 



( E'l.ATK ()") 



Cystosori one to several in .1 ii II. pri (louiiii.intly nt' 

 the slia|)0 of hollow sjiheres or ellipsoids, luit often 

 extremely variable in size anil shape; presenee of 

 oonimon eiiveloj)lng membrane doubtful. Resting 

 spores oval, ellii)soidal. j)vriforni, pyramidal and 

 urn-sliapeil with yellowish-brown to brown, thin, 

 smooth or \errueose walls; with or without .ipie.il 

 eollar; produeinj;: a siniilf bitlaiiellate, heteroeont 

 zoos])ore in gerniin.-ition. Kv;nieseent thin-w.illed 

 zoosporansjia sm.ill. I'l.isniodia one to several in a 

 eell. large or small: sehi/.otjony present ( ?) or lack- 

 injr; produeinji a sinj;le cystosorus. 



This genus includes at present only two species 

 which have been reported in moist and damj) locali- 

 ties in Europe. England, and the U. S. A. Of these 

 two, iS. r eronicac appears to be more common and 

 has been frequently studied cytologically. Nonethe- 

 less, many of its critical develo])niental stages are 

 still im)>erfeetly known, and there has been consid- 

 erable controversy relative to many of its cytologieal 

 details. Germination of the resting spores had not 

 been observed until very recently. Blomficid and 

 .Scliwartz ('10) re|)orted the jjresence of amoebae in 

 a sterile infusion of 1 erunica leaves which had been 

 inoculated with i)ortions of dead tumors. Since this 

 infusion was thus no longer sterile and soon became 

 invaded with bacteria, molds and other organisms 

 from the tumors, the uninucleate amoebae which they 

 found after fourteen days in the bottom of the test 

 tube may not relate to S. J'eronicae at all. In S. radi- 

 cali.s. Cook and .Schwartz likewise failed to observe 

 germination, but among diseased root hairs they 

 found anteriorly uniflagellate zoospores which they 

 assumed relate to their s))eeies. However, they did 

 not follow the development of these zoosjiores into 

 mature thalli. On the other hand. Barrett foinid that 

 the zoospores from sporangia are distinctly bitlagel- 

 late and heteroeont. He also succeeded in germinat- 

 ing the resting spores, but has not yet determined 

 the number of flagella on such zoos))ores. I.edingham 

 ('3S). p. 1-3) found that zoos|)ores from resting s))ores 

 of .S'. t'eronicae also are biflagellate and heteroeont. 

 Cook ('33) stated that the resting s))ores form a sin- 

 gle amoeba or zoospore, but it is quite probable that 

 the multinucleate spores rejiorted by Maire and 

 Tison (fig. 49-.5I) may give rise to several zoo- 

 spores. 



-Vs the primary uninucleate amoebae of .S'. I'l-ro- 

 nica (tig. 9) increase in size within the host cell, their 

 nucleus divides, and multinucleate |)lasmodia are 

 soon formed (fig. 11-1.5, 22). Hy the time the eight- 

 nucleated stage has been reached, the plasmodia may 

 function as schizonts and split off uni- and multi- 

 nucleate meronts (fig. 23. 2 J), according to Maire 

 and Tison, The multinucleate meronts may in turn 

 undergo schizogony into uninucleate segments be- 



fore further mitoses occur. The unimicleate meronts 

 are ciiuiv.ilent to the primary amocb.ii' and ni.iy thus 

 begin the eyi'le .mew. while the scliizont from which 

 they are derived ])asses into the s))orogonie jihase of 

 (levelojimcnt, in the opinion of .Maire and Tison. 



It is to be noted, however, th.-it these workers have 

 ncxcr observed the actu.-il s))litting oft' of meronts, 

 .ind their re])orts on the presenee of schizogony are 

 based only on the .ipiiea ranee of constricted plas- 

 modia (fig. 2.i. 2 1-) .-md the grc.-it abuiulance of uni- 

 luiele.ite amoeb.ie in infected cells. The Latter may 

 well be the result of nuiltiple infection, while stages 

 such as are shown in figures 23 and 21' may possibly 

 rei)resent, as Maire and Tison earlier interpreted 

 them, fusions of uni- and bimicleatc amoebae with 

 nuiltinucleate |)lasniodia. \\'hile the author readily 

 admits the possibility of schizogony, he does not con- 

 sider the evidence so far ))reseiited as sufficiently re- 

 liable to have conclusively settled the jtroblem. In 

 this connection it is significant to note that schizog- 

 ony has not been recorded in species, such as S. radi- 

 cal'is, where the process if present could be readily 

 observed in living material. 



Tl'.e vegetative phase is terminated by the so- 

 called transitional stage after which follow cleavage 

 and meiosis, as has been described in Chajiters \\ 

 and III. The plastic cleavage segments or incipient 

 resting spores become associated in a globular mass 

 (fig. H) and resemble myxamoebae in a pseudoplas- 

 modium. By mutual readjustment they soon move to 

 the periphery (fig. II) and thus form a hollow 

 s])here or ellipsoid. At this early stage the center of 

 the mass is filled with a viscuous fluid, doubtless a 

 residue of the plasmodium which is not used up in 

 cleavage. Whether or not this substance rejiresents 

 extraneous waste material which is dumped into a 

 central vacuole in the dediiferentiation of the proto- 

 ))lasm ])reparatory to sporogenesis as in various pro- 

 teomyxean species is not certain. Maire and Tison 

 stated that it has an osmotic coerticient and exerts 

 centrifugal pressure on the s))ores whereby they are 

 |)ushed to the periphery of the mass. 



.Shortly after their arri\al there, the individual 

 s])orcs develop delicate walls wliic'h thicken and turn 

 brown with maturity and often become verrucose. No 

 evidence of cellulose or i)ectin M-as found in these 

 walls by Maire and Tison. By mutual compression 

 the spores usually become iientagon.-illy and hex- 

 agoiially |)yramidal in shaiie with convex external 

 and slightly concave intern.-il surfjices. According to 

 ^\'inge. a eollar is formed .at the ;i))ex or external 

 surface (fig. 18), but this structure has not been re- 

 corded by other workers. Occasional bi- and trinu- 

 cleate spores occur (fig, ■19-.51). which may have 

 arisen by incomplete cleavage or by subsequent di- 

 vision of the spore nucleus (fig. .50). 



It is to be partieul.irly noted that in none of the 

 figures and descriptions of Blomficid and .Schwartz 

 or Maire and Tison which illustrate the aggregation 

 of incipient resting spores and their transformation 

 into cystosori is there evidence of a distinct, common 

 eiivelo))ing membrane around the sorus. Likewise, it 



