sept. 16,1918 Tissue Invasion by Plasmodiophora brassicae 
569 
Sorodiscus CALiyiTRiCHis. —This parasite produces swellings on 
Callitrichis autumnalis and C. vernalis. The galls are round or somewhat 
elongated. They are usually smaller than those of Sorosphaeta veronica. 
The distribution of the casual organism in small groups of cells scattered 
about in the tissues of the inner cortex (7) shows a close resemblance 
to the distribution above described for P. brassicae. Here, again, infec¬ 
tion has spread to all sides of the stem. The round or slightly elongated 
gall may be looked on as a short spindle, and might be caused by an 
infection similar to that produced by the clubroot organism, provided 
the parasite travels very slowly through the tissues. 
Tetramyxa parasitica. —Goebel (<5) has described and pictured the 
galls of this parasite on Ruppia rostellata Koch. They occur on both 
stems and leaves and are small and round in shape. It is not possible 
to determine from his description or his pictures just what tissues are 
involved. The statement that the region of infection is surrounded by 
noninfected cortical tissues is very suggestive. What seems to be 
another species of Tetramyxa has been described by Molliard (12) on 
Triglochin palustre L. This species also parasitizes T. maritinum K, and 
has been studied by Maire and Tison (11). These authors picture cross 
and longitudinal sections through the galls. The distribution of the 
parasite in the tissues is strikingly like that of P. brassicae. Maire and 
Tison have described this fungus as a new genus, Molliardia, differing 
from Tetramyxa in that it does not form spores. But the failure to 
observe spores is no proof that spores do not occur, and the writer agrees 
with Winge (15) that, for the present at least, it should be left in the 
genus Tetramyxa. 
Ostenfeudiella diplantherae. —This parasite which was described 
and named by Ferdinandsen and Winge (5) causes swellings on the stems 
of Diplanthera wrightii Aschers. The galls produced suggest a method 
of infection similar to that found for P. brassicae . The swelling extends 
around the stem and the parasite is confined to the cells of the inner 
cortex. In the upper and youngest part of the overgrowth only un¬ 
inucleate amebae are present, while in the more mature portions of the 
gall plasmodia containing many nuclei are found. This suggests that 
the disease spreads up the stem. 
Ligniera 'graminis. —Two species are included under the genus 
Ligniera: Ligniera graminis (Schwartz) Winge and Ligniera junci 
(Schwartz) Maire and Tison. The genus differs markedly from other 
genera of the Plasmodiophoraceae in that it does not produce galls. 
But this failure to stimulate abnormal growth in host tissues is probably 
connected with the nature of the tissues infected. Only cortical cells 
are attacked. In all the other genera deeper and more actively growing 
cells are infected. 
From the above discussion it will be seen that the galls produced by 
Plasmodiophora brassicae , Sorosphaera veronica , Sorodiscus callitrichis , 
