6 Levi Otto Gratz 



is heavily infected with the causal organism. Under these conditions 

 germination of the seed may be prevented, or the plants may be killed 

 outright, but usually most of them will recover partially. In light attacks 

 there may be no toppling over. If the moisture content of the soil is 

 high, the plants may not even wilt. In a very few days, the cortex will 

 be destroyed partially or completely and the second stage of the disease, 

 wire stem, will be evident. Now is to be found a crooked, dwarfed plant 

 with a peculiar tough, woody, wire-like stem (Plate I). Small brownish 

 lesions, similar to those caused by this fungus on potato stems, are seldom 

 found, but usually the entire basal part of the stem is affected. In the 

 earlier, or dam ping-off, stage, the mycelium of the fungus is easily demon- 

 strated at the margin of the lesion. When the wire-stem stage has 

 appeared, it is often impossible to do this especially in the later period of 

 the disease. 



ETIOLOGY 



Nomenclature, and review of literature 



The disease under consideration is caused by Corticium vagum B. & C. 

 The Corticium stage of this fungus was first recorded by Rolfs (1903, 

 1904). Judged by its parasitic mode of life and morphology, it was 

 considered sufficiently different from Corticium vagum B. & C to con- 

 stitute a new variety and was designated Corticium vagum var. solani 

 Burt. Burt (1918) later identified the Corticium causing the potato 

 disease as the common Corticium vagum B. & C, thus reducing the variety 

 to synonymy. Duggar (1915, 1916) reviews extensively the early Euro- 

 pean literature, and concludes that the fungus causing damping-off in 

 this country is the same as Rhizoctonia solani Ktihn, which causes lesions 

 on potato stems in Europe. He states that the fungus is distributed 

 throughout the United States, Canada, and Europe, has been reported 

 from Brazil, France, Ireland, Australia, Great Britain, New Zealand, and 

 Japan, and probably has been observed in all its stages in the more humid 

 regions of India. Peltier (1916) gives an extensive table, setting forth 

 the distribution of the disease and its many scores of hosts in the United 

 States and other countries. Matsumoto (1921) was concerned chiefly 

 with specialization of Corticium vagum, both in his review of literature 

 and in his researches. This phase is discussed later in this paper. 



Morphology and physiology 

 The mycelium 



The mycelium of the fungus causing wire stem of cabbage is, both within 

 the host and in culture, the typical, septate, broad, hyaline, branching 

 "sterile fungus" mycelium which Atkinson (1895), Rolfs (1902, 1904), 

 and others have accurately described. The diameter of the hyphae as 

 computed by measuring fifty strands of a five- days-old culture is approxi- 



