INJURIES INDUCED BY PLANTS 39 



MYXOMYCETES, OR SLIME-FUNGI 



Amongst the Myxomycetes, several though the number is a 

 small one live as parasites, and cause peculiar swellings to form 

 on the roots of their host-plants. To these belongs Plasmodio- 

 phora Brassicce} which causes " club-root"* in cabbages, &c. The 

 roots and lower parts of the stems of cabbages which are attacked 

 by this parasite exhibit excrescences which vary in size but are 

 often as large as one's fist. These soon decay, and the enfeebled 

 plants frequently fail to give any return. The disease is com- 

 bated, on the one hand, by burning the stumps of all infested 

 cabbages, so that the parasite is prevented from spreading in 

 the soil, and, on the other, by ceasing to cultivate cabbages for 

 some years on ground where the disease has appeared. 



Alder-roots, even when very young, are generally beset with 

 much-branched tuberous outgrowths, in whose 

 cells Woronin has discovered a fungus which 

 he has named Schinzia Alni. 



Recently Moller 2 has referred the plasmo- 

 dium-like structures which occur in the cellu- 

 lar tissue of the excrescences of the roots of 

 alders to a Myxomycete belonging to the FIG. 9. Excrescence 

 genus Plasmodiophora, which he calls Plasmo- ^^ roo ^ u f ^ 



diophora Alni. Whether this is identical with Schinzia Alni. 



Schinzia Alni, or distinct from though oc- 

 curring simultaneously with it, cannot be decided without 

 further investigation. 



The tubercles on the roots of Leguminosce^ and Elceagnece, 

 in whose parenchymatous cells plasmodium-like structures occur, 

 also require to be further investigated. 



1 Woronin in Pringsheim's/^r^., vol. xi. p. 548. 



2 H. Moller, " Plasmo diophora AM" Ber. Deutsch. bot. Ges., i88s,Pt. 3, 



p. 102. 



* [Often termed " Fingers and Toes " and "Anbury." ED.] 



f [These tubercles are caused by symbiotic organisms of quite different 



nature from Myxomycetes. See Phil. Trans. 1887 and Proc. Roy. Society, 



1889. ED.] 



