264 ASCOMYCETES. 



These develop to strong mycelial threads if they reach any 

 source of nutriment, such as disorganized bodies and particularly 

 dead plants. On any other substratum the germ-tubes never 

 pass beyond a rudimentary stage. The germ-tubes developed 

 in water cannot make their way into living plants. If, however, 

 grown in suitable nutriment, the mycelial threads are smaller 

 and capable of penetrating as parasites into suitable hosts. This 

 they are able to do because they give off a fluid which enters 

 into and kills living plants. The dead parts of the plants 

 serve as nutriment to the fungus, which makes its way into 

 the tissues and causes death of cells in direct contact or im- 

 mediate neighbourhood. The deadly fluid separated by the 

 fungus contains, as an essential constituent, an enzyme soluble 

 in acid solutions and capable of dissolving the cell-walls ; also 

 a number of imperfectly known organic and inorganic acids 

 and salts, amongst which oxalates can certainly be proved. 

 The mycelium generally penetrates parts covered only by cuticle 

 or a thin periderm. It does so by hyphal branches which grow 

 into the air till they reach some suitable host ; then, stimulated 

 by the pressure, they give off characteristic organs of attachment, 

 which secrete a cell-killing fluid and cause disorganization of 

 the place attacked ; they derive nourishment from the products, 

 and give off branches which penetrate into the plant." 



Conidia capable of germination are never produced, though 

 rarely tiny spermatia or conidia incapable of germination are 

 abjointed from the mycelium. 



A Jjotrytis-stage is certainly never present in the life of 

 this species. 



Set. sderotiorum is one of the worst enemies of cultivated plants. 

 De Bary observed total or partial death resulting from it to 

 the following plants : Phaseolus vulgaris, Petunia nyctagitvijlora 

 and P. violaccac, Suliinnin tuberosum, Zinnia <'/<>/(/ /is, Hclinntlii/x 

 tubcrosi/s, and Daucus Carota. It has also been found on species 

 of Brassica, Beta, Cichormm, DnJiJin, Topinambur, etc., and on 

 seedlings of numerous other dicotyledons. It is thus evident 

 that many and varied plants, belonging to widely removed 

 families, may serve as hosts ; on the other hand the fungus 

 avoids certain plants, and is known to injure species in one 

 locality, which it avoids in another. 



De Bary regards a destructive canker on hemp in Eussia 



