i6o 



DISEASES OF CULTIVATED PLANTS 



Black root rot (Thielavia basicola, Zopf) was first met 

 with in England on the roots of peas, and called Torula 

 basicola by Berkeley and Broome. Four kinds of fruit have 

 been described, the highest of which is an ascigerous form 

 discovered in Germany by Zopf, on the root of a Senecio. 

 Some doubt was at one time entertained as to whether the 



FIG. 41. Thielavia basicola. i, diseased pea 

 root ; 2, portion of first conidial stage (Milowia) ; 

 2 x , free conidia of same ; 3, second conidial stage 

 (Torula); 3X, a conidium of same breaking up 

 into cells ; 4, ascospores ; 5, perithecium on winter 

 fruit ; 6, ascus containing 8 spores, from winter 

 fruit. Fig. i nat. size ; remainder highly mag. 



fungus was a true parasite, and although capable of existing 

 on manure and dead plants as a saprophyte, recent observa- 

 tions and experiments have proved that under certain condi- 

 tions, more especially on badly drained or water-logged soil, 

 the fungus acts as a very destructive parasite. 



The fungus has been found parasitic on numerous different 

 kinds of plants belonging to widely separated families, as 



