414 BOTANICAL GAZETTE [NOVEMBER 
Plasmodiophora, Sorosphaera, and Tetramyxa. The new genus includes L. 
radicalis, which is new, L. Junci (Schwartz) (Sorosphaera Junci Schwartz), 
and L. verrucosa, also new. 
OsBORN” gives an account of the development of the interesting form 
Spongospora subterranea, causing the corky scab of potatoes. Penetration 
of the organism into the host cell was not observed, nor was it possible to 
infect sound potatoes with spores. The first stage observed consisted of an 
amoeba containing a single nucleus, which had a membrane, chromatic gran- 
ules, and a deeply staining karyosome. In the early stages nuclear division 
is followed by division of the amoeba, so that a number of independent amoebae 
are found in the same host cell. The parasites occur in the cambium, and 
when the parent cell divides, one or more amoebae are included in each daughter 
cell, in the manner described by NAWASCHIN for Plasmodiophora, and by BLOoM- 
FIELD and Scuwartz for Sorosphaera. The division of the nuclei during this 
stage is of the type characteristic of the group. The chromatin forms a ring 
around the karyosome; both the ring and the karyosome then divide, and the 
halves move toward the poles, where the halves of ring and karyosome unite 
into a deeply staining mass. The nuclear membrane constricts between the 
masses, and finally divides at the point of constriction, leaving each chromatic 
mass enclosed in a separate membrane. No fibers or polar radiations were 
observed. At a later stage many of the amoebae are multinucleate, and when 
the food content of the host cell is exhausted, the amoebae coalesce to form a 
plasmodium. At this time the chromatin of the nuclei disappears and chro- 
matic material appears in the protoplasm. When the nuclei appear organ- 
ized again, they contain a chromatin network but no karyosome. The author 
is inclined to believe that the new nuclei are constructed de novo. This stage 
is soon followed by fusion of nuclei in pairs, and a period of nuclear growth 
previous to spore formation. Two karyokinetic divisions take place, after 
which the protoplasm is rounded up into uninucleate spores 
In a later paper Marre and Tison*' give the results of further observations 
on Sorosphaera, Tetramyxa, Ligniera, and Mollierdia, some of which differ 
in some points of their development from other forms of this group. Teéra- 
myxa parasitica has multinucleate plasmodia during the phase representing 
e schizogenous stage, the nuclear divisions not being accompanied by ¢ | 
division. The chromidial stage, prominent in other forms, is lacking here. 
At the secre of spore formation, me plasmodia break up into uninucleate 
masses. result of two mitotic divisions, 
and divide by constriction into four uninucleate spores. In this form, 45 
* OsBorn, T. G. B., Spongospora subterranea (Wallroth) Johnson. Ann. Botany 
25 1327-341. pl. 27. 1911. 
* Marre, René, et Tison, ApRIEN, Nouvelles recherches sur les plasmodiopho- 
races. Ann. Myc. 9:226-246. pls. 10-14. fig. 1. IgIr. 
