180 THE MVXOMVCETES OF l'ICTOU(;OUNXV.— .MOORE, 



i'l^ee or (2) exteruallv on columnar or membranous sporopliores 

 or (3) in closed capsnles or sporangia. In germinating the 

 spores produce amoeboid bodies wliicih pass tlirtnigli a ciliated 

 stage and which eventually fuse to form a multinuclear proto- 

 plasinic mass, the plasmodium. whicli give?; rise to the frnctiii- 

 cations. 



Sub-class 1. PHYTO:\rYXTX.E.— AFature fruit bodies 

 converted into an aggregation of free spores. Parasitic in cells 

 of living plants. 



Sub-class 2. EXOSPOKE J^]. — Spores formed superficially 

 on membranous or columnar sporophores. Saprophytic. 



Sub-class 3. MYXOGASTEES.— Spores formed within 

 S|X)rangia. Saprophytic. 



PHYTOMYXIN^ Schrotcr. 

 Parasitic in the cells of living plants. The spores are formed 

 by 1\he simultaneous division of the mature plasmodium and lie 

 free in the cells of the host. 



Genus, Plasmodiophora Woronin,. 



The only representation of the genus and sub-class which 

 has come under my observation is : 



1. Plasmodiophora hrassicw Woronin. — This species is 

 parasitic on various cruciferse such as the turnip, cabbage, rape 

 and kale, producing in these plants the disease popularly known 

 as *' Club root." T|he roots of infected plants exhibit irregular 

 and distorted growth, become covered with irregular ])r()tuber- 

 ances and swellings and eventually decay. A section throug^h 

 one of these swellings shews the enlarged parenchymatous cells 

 almost completely filled either with plasmodium ( ?) of the 

 parasite or with the spores. Tluse are splierical :ind about 1.5//. 

 in diameter. 



AYhat is probably the same parasite also occurs here on s]ie- 

 cies of wild mustard and is pretty generally distril)nted through- 



