132 



THE FUNGI WHICH CAUSE PLANT DISEASE 



Mitnila sclerotiorum Rost.^* 

 which causes a disease of alfalfa in 

 Denmark is the only pathogen of 

 the family. The infected plants die 

 and later the roots and stems be- 

 come filled with black sclerotia 

 which lie dormant about a year. 

 Fig. 89. — Mitrula. B, habit UpOn resuming growth they be- 



sketch; F, asci. After Schroter. , , i- i . j i 



come covered by light red eleva^ 

 tions, which bear small light red ascocarps. 



Rhizinacese (p. 131) 

 Key to Genera of Rhizinacese 



Spores elliptic or spindle-shaped" 



Without rhizoid-like structures 1. Psilopezia. 



With rhizoid-like structures 2. Rhizina, p. 132. 



Spores globose 3. Sphserosoma. 



Only one genus, Rhizina, causes 

 disease. 



Rhizina Fries with some eight 

 species is recognized by its- crust- 

 formed, sessile, flat ascophore with 

 root-like outgrowths from the lower 

 side. Fig. 90. Asci cylindrical, 8- 

 spored, opening by a lid; spores one- 

 celled, hyaline; paraphyses many. It 

 is often purely saprophytic, growing 

 in burned-over spots in forests. 



R. inflata-(Scha£E) Quel."'" 



IS 



counted as the cause of serious root ^'°- 90— Rhizma mflata. B, asco- 



j- r J i i . „ "^'T '™'" below; C, asci and 



diseases Ot forest trees, especially paraphyses. After Schroter and 



conifers, in Europe. The fungus also '^"•*^°^- 

 occurs in Asia and America. 

 R. undulata causes death of fir seedlings.^ 



