The Plasmodiophoraceae and their Relationship to 
the Mycetozoa and the Chytrideae. 1 
BY 
E. J. SCHWARTZ, M.A., B.Sc. 
With Plate XII. 
S INCE the publication in the Annals of Botany, in 1911, of an investiga- 
tion of the life-history and cytology of Sorosphaera Graminis ( 25 ), a 
great deal of work has been done on the Mycetozoa and Plasmodiophoraceae, 
and several papers have been published describing the cytology of various 
species and discussing the relationship between these two families. Pavillard, 
in the ‘Progressus Rei Botanicae’, 1910, gives an excellent account of the 
position at that date, and concludes that the Plasmodiophoraceae are 
a branch of the Mycetozoa that has become modified owing to having 
taken to a parasitic mode of life. Maire and Tison (13 and 14 ), in 1911, 
combat this view, and suggest that the Plasmodiophoraceae should form 
a separate family, which they consider probably owes its origin to the 
Chytrideae. Osborn ( 20 ), on the other hand, in his paper on Spongospora , 
lays stress on the similarities between the Plasmodiophoraceae and Myce- 
tozoa, and describes a karyogamy similar to that observed by Jahn and 
Kranzlin in the Mycetozoa. 
The present paper is the outcome of the study of many species of both 
the Plasmodiophoraceae and the Mycetozoa, and, while admitting that 
these families are related, I am in agreement with the opinion expressed 
by Maire and Tison that their differences are so great that the Plasmodio- 
phoraceae should form a separate order intermediate between the Mycetozoa 
and the Chytrideae. I do not think that the differences between these 
families can be accounted for by the parasitic mode of life adopted by the 
Plasmodiophoraceae. 
The Plasmodiophoraceae. 
This family comprises a number of multinucleate amoeboid organisms, 
which live as parasites on various Phanerogamic plants ; the best known, 
and perhaps the commonest, member of the family is P. Brassicae . The 
1 This thesis, together with the work on the Plasmodiophoraceae previously published, viz. 
Root Diseases of the Juncaceae ; Tumours on Veronica Chamaedrys ; Life-history and Cytology of 
Sorosphaera Graminis , was approved for the Degree of Doctor of Science in the University of London. 
[Annals of Botany, Vol. XXVIII. No. CX. April, 1914.] 
