Relationship to the Mycetozoa and the Chytrideae . 231 
The genus Spongospora, Brunch. 
suhterranea has been described by Osborn (20), and agrees in most 
respects with other genera. As before stated, Osborn maintains that there 
is a complete disappearance of nuclei in the akaryote stage, and that fresh 
nuclei (reproductive) are formed on different sites. These reproductive 
nuclei fuse in pairs, and the resulting nuclei undergo two mitoses prior to 
the formation of spores. This karyogamy, observed by Osborn, has not 
been noted in any of the other genera. The vegetative nuclei divide in the 
manner peculiar to the Plasmodiophoraceae. Osborn, however, states that 
the chromatin is in the form of a ring around the elongated karyosome, 
whereas careful focusing shows that it is in reality an equatorial plate. 
Osborn was unable to get the spores to germinate, but Massee (15) states 
that he has seen a germination, the spore giving rise to a single myxamoeba. 
The genus Ligniera, M. and T. 
This genus, which is closely allied to Sorosphaera , was formed by 
Maire and Tison (13) to include those members of the Plasmodiophoraceae 
in which the spore-clusters are most usually of ellipsoidal and irregular 
shapes and are rarely spherical. A common characteristic of the members 
of this genus is that they do not give rise either to hypertrophy of tissue 
or to nuclear degeneration in the host-plant. To this genus the species 
described by myself and named Sorosphaera Junci and 5. Graminis have 
been transferred. 
Other species at present included in the genus are: L . radicalism 
M. and T., found on roots of Callitriche stagnalis ; L. verrucosa , M. and T., 
found on roots of Veronica arvensis. 
To the above species three new ones, recently found by myself, have 
now to be added — viz. L. Bellidism L. Menthae , and L . Alismatis. All the 
Ligniera agree closely in their life-histories and cytology, but, owing to the 
fact that they do not cause hypertrophy in their host-plants, and for other 
reasons referred to later, they are not so suitable for the observation of 
cytological details as are the members of the other genera. All the species 
of this genus are root parasites, and the infection in all cases takes place 
near the root apices. The infected cells, which are confined to the outer 
cortex of the root, are frequently found in longitudinal rows. In many 
cases the amoeboid stage of the organism is only to be found in the youngest 
roots. Root-hairs may also serve as channels for infection, but in this case 
the amoeba does not spread the infection beyond the cell which gives rise 
to the hair. The parasite may complete its life-history in the root-hair by 
the formation therein of a row of spores. Schizogony is rare, and the 
akaryote stage is seldom seem, it being probably of but short duration, as 
Osborn suggests. 
