SOHOIIISI IS 



n 



possibly nioro tli;iii oiio zoospore in ■;crinin;iti<in. Zoo- 

 sporangia unknown. I'lasnuuiia ono to several in a 

 coll. large or small; sehizogony laekinji or doubtful 

 in some species. 



Siinnliscim inehuies at present three or jiossibly 

 four species (see MrinhraiiosDriix in this eoniieetiou ) 

 which h;ivc been reporteil from Russia. Norway. 

 Sweden, .South Africa and the United States. They 

 occur under fairly moist and aqu.atic coiuiitions. (i.-ir- 

 asitize algae and hiiilier i)lants. and cause marked 

 hypertrophy of the host in the form of galls or 

 tumors which may be uni- or nuilticellular. Since 

 most of these species have been studied only from 

 fixed and st.-iined material many of the critical 

 dcvclopnuiit.il stages are (loorly known, and the va- 

 rious claims concerning the ])rcsence of sexviality. 

 karyogamy. meiosis. alternation of haploid aiul dip- 

 loid generations, etc.. arc obviously based on inade- 

 quate cytological data. 



Furthermore, the outstanding character of the 

 genus, namely, oval and almost circular, flat and disc- 

 sha)>ed cystosori composed of two closely jiressed 

 layers of resting s])ores. has been seriously ques- 

 tioned. In the type species, iS'. Callitrichis, the cysto- 

 sori m;iy sometimes be hollow spheres, while in S. 

 karliiifiii they may vary from hemisi)herical multi- 

 nucleate monads, diads. triads, tetrad, flat discs, and 

 elongate linear series of spores to almost hollow 

 spheres (PI. 8, fig. 11-21). In all of the s])ecies. 

 however, the majority of cystosori are flattened and 

 disc-like. M'hile A\'inge ('13) regarded Sorodixciis as 

 a distinct genus he nonetheless pointed out that its 

 similarity to Soros phaera is so great "tiiat it would 

 seem most reasonable to unite them into one genus." 

 Later, however, in a communication to Cook ('31. 

 p, 318) he said "that the spore masses are so char- 

 acteristic in Snrodi.scu.1 that it would be wrong to put 

 it in the s;ime genus as Soro.iphai'ra." Palm and 

 Burk (33). on the other hand, regarded Sorodisciis 

 as a syiu)nyni of the latter genus. 



Schizogonv has not been observed in Sorodi-icus, 

 although Winge believed that the widespread distri- 

 bution of amoebae in the galls formed by -S'. Calli- 

 trichis suggests its occurrence. Whether or not a 

 common enveloping membrane is jircsent around the 

 cystosori in all species is uncertain at i)resent. Fur- 

 thermori-, little is known about the origin and devel- 

 o|)mcnt of this membrane in the s]>eeies in which it 

 has been reported to occur. In S. Callitrichis, accord- 

 ing to Winge. the resting "spore-wall divides into 

 two layers of which the outer one merges into that 

 of the neighboring spores (fig. 31. 32) so that it 

 gives one the inij)rcssion of the spores being de- 

 posited in a common substance." According to this 

 statement no distinct and separate wall is formed, 

 and tlie s))ores are merely adherent by the outer 

 layer of their walls. Figure 33, however, shows an 

 enveloping membrane. Cook considered Winge's in- 

 terpretation incorrect and stated that in S. radici- 

 colus a distinct wall is laid down around the cysto- 

 sori. He did not. however, present any evidence 

 about its origin — whether it consists of the original 



liouuding mcmbr.inc of the plasmodium ])riscut at 

 the time of clcav.-igc or is dc])ositcd subsecpiently by 

 the m.ituring resting sjjorcs. Furthermore, his fig- 

 ures 23 and 21 of mature spore cakes do not show a 

 separate common w.all .-iround the sjjores. In S. kar- 

 lliif/ii no evidence of an enveloping membrane has 

 vet been observed (fig. 11-21). 'I"hc )iresence of 

 such a membrane in the genus as a whole is thus still 

 open to serious question, and if ))rcscnt its origin and 

 method of development arc certainly in need of in- 

 tensive cytological study. 



^^'inge and Cook differed also in their observations 

 relative to sporogenesis and the stage at which meio- 

 sis occurs. In -S'. Callitrichis numerous binucleate 

 segments or s|)ore mother cells are formed by ])ro- 

 gressive cleavage of the plasmodium (fig. 27). and 

 these segments (fig. 28 and 29) then divide once to 

 form groups of s|)ores in twos (fig. 30), according to 

 Winge. These groups of incipient resting s])ores soon 

 aggregate together, deposit two-layered walls (fig. 

 28, 29). and thus form the characteristic cytosori 

 (fig. 33). In iV. radicicolus, however, according to 

 Cook ('33. p. 207). the j)rimary cleavage segments or 

 sjiore mother cells (fig. 20) divide twice to form four 

 instead of two inci])ient resting spores. Cook did not 

 show clearly how these united to form the cystosorus 

 and an enveloping wall. It may be that the two 

 species actually differ in this respect, but further 

 study is necessary to determine this point. If Winge's 

 and Cook's accounts are correct Sorodiscus shows 

 marked similarity to Sorosphaera by the ])resence of 

 s])orc mother cells which divide into diads and tet- 

 rads and subsequently aggregate into sori. 



S. CALLITRICHIS I.aperheim and Winpe, I.e.. p. 33. 

 PI. 1, fig. 9, 1(1; PI. -'; PI. 3. fi;:. 43-63. 



Cystosori up to 10 in a cell, usually circular, flat 

 and "disc-shaped. 30-1-5/. X 10-6.5 )x X 12-11/1, 

 rarely spherical and hollow; composed of U|) to 200 

 resting spores usually arranged in two layers and 

 closely pressed together ; outer layer of spore walls 

 continuous {!). Resting spores urn-shaped in longi- 

 tudinal section and hexagonal in cross section, t- .5 /n 

 X 6-7 //. with smooth hyaline walls surmounted at 

 the al>ex by a collar; germination unknown. Zoospo- 

 rangia and zoosjjores unknown. Plasmodia one to 

 several in a cell, large. 10-00 /x in diam., each form- 

 ing one cystosorus; schizogony doubtful or lacking; 

 cleaving at maturity into binucleate segments or 

 sjjorc mother cells which divide once (?) into two 

 resting s])ores. 



P.irasitic in Callitriche icrnaVis in Norway ( I.a- 

 gerheim and Winge, I.e.) and C. autiimnalis in Russia 

 ( KareltsehikotT and Ros.inoff. '70) and Sweden 

 (Ostenfeld). causing globular galls uj) to 3X''' mm. 

 on the primary and secondary axes. 



This species was first recorded in 1870 by Ka- 

 reltschikoff and RosanofT who mistook the cystosori 

 for cystoliths and com))ared them with those present 

 in the L'rticaeeae. although Rosaimrt was of the 

 o|)inion that they might be rcmnauts of a parasitic 

 mycelium. According to Winge, Lagerheim collected 



