238 Schwartz . — The P lasmodiophoraceae and their 
From a cytological point of view it is clear that these organisms are 
closely related to the Plasmodiophoraceae. The great similarity of the 
vegetative nuclear division, the somewhat similar akaryote stages, the 
karyokinetic divisions of the reproductive nuclei are all evidence of relation- 
ship. As differences we may note the formation of a membrane around 
the developing sporangium, and the fact that this body contains the spore 
mother-cells, and not the spores themselves. On germination the nuclei of 
these mother-cells undergo the karyokinetic divisions, whereas in the 
Plasmodiophoraceae these two divisions preceded the resting stage. Like 
the Mycetozoa, these species of Olpidium have both the vegetative and 
the reproductive forms of nuclei. The so-called spores of some of the 
Mycetozoa may, in reality, be * sporangia ’, in that they give rise to more 
than one swarm-cell on germination, as for example Ceratiomyxa or 
Comatricha . The balance of the evidence of relationship seems to me 
to show that the Plasmodiophoraceae should form a separate class inter- 
mediate between the Chytrideae and Mycetozoa. 
Summary and Conclusions. 
t. The root parasites of Beilis perennis , Mentha Pidegium, and Alisma 
Plantago are members of the Plasmodiophoraceae belonging to the genus 
Ligniera . 
2. The ‘ cruciform 5 type of vegetative nuclear division, and the presence 
of the akaryote stage is constant throughout the Plasmodiophoraceae, but 
both are lacking in the Mycetozoa, but are found in Olpidium . 
3. The nuclei of the Plasmodiophoraceae, Mycetozoa, and Chytrideae 
are of two types : vegetative and reproductive. 
4. There is an absence of karyogamy prior to spore formation in 
all three families. 
5. In the Mycetozoa the vegetative and reproductive nuclear divisions 
are karyokinetic. 
6. The Plasmodiophoraceae, though closely related to both the Myce- 
tozoa and Chytrideae, are best considered as a separate class. 
7. The spore mother-cells in the zoosporangium of Olpidium each give 
rise to four zoospores. 
8. There is a conjugation in pairs of the zoospores of the Chytrideae. 
9. There is a conjugation of the myxamoebae and a nuclear fusion in 
the Mycetozoa. 
Bibliography. 
1. Blomfield and Schwartz : Some Observations on the Tumours of Veronica Chamaedrys 
caused by Sorosphaera Veronicae. Ann. of Bot., vol. xxiv, 1910. 
2. Griffon and Maublanc : Notes de pathologic vegetale et animale. Bull, ch 1 . Soc. Myc. de 
France, vol. xxvi, 1912, p. 469. 
