CHAPTER VIII 



MYXOMYCETES. SLIME MOLDS 



I. PHYTOMYXALES (PHYTOMYXACE^E) 



In the family Phytomyxaceae are" grouped the few disease- 

 producing organisms among the Myxomycetes. The family is 

 characterized by the production of naked masses of protoplasm 

 (plasmodia) within the cells of the host. The plasmodium gives rise 

 simultaneously, or by a successive differentiation, to sphaeroidal 

 spores, and the germination of the spore produces a motile swarm 

 cell, by means of which distribution of the organism is effected. 

 Generic differences are found almost wholly in the relation of the 

 spores one to another, whether single or grouped. Plasmodiophora 

 Brassiccz is the only well-known species of economic importance. 



II. CLUB ROOT OF CABBAGE AND OTHER CRUCIFERS 

 Plasmodiophora Brassiccz Wor. 



EYCLESHYMER, A. C. Club-root in the United States. Journ. Myc. 7 : 79-87. 



pis. 15-16. 1892. 

 HALSTED, B. D. Club-root of Cabbage and its Allies. N. J. Agl. Exp. Sta. 



Built. 98: 1-16. Jigs. 1-13. 1893. 

 NAWASCHIN, S. Beobachtungen tiber den feineren Bau. u. Umwandlungen 



von Plasmodiophora. Flora 86 : 404-427. pi. 20. 1899. 

 WORONIN, M. Plasmodiophora Brassicae. Jahrb. f. wiss. Bot. 11 : 548-574. 



pis. 19-24. 1878. 



The club root, or club foot, is an unsightly and destructive root 

 disease of crucifers which has been known in Europe for con- 

 siderably more than a century. In England it is commonly called 

 fingers and toes, anbury, etc. (Germany, Kohlhernie ; France, 

 maladie digitoire). Our knowledge of the causal relations of a 

 Myxomycete, Plasmodiophora, to the disease is primarily based 

 upon the excellent researches of Woronin published in 1878. 



Habitat relations. In Europe the fungus is quite generally 

 distributed throughout the market-gardening sections. In 1876 



97 



