362 Diseases of Greenhouse Crops 



sudden dying of the plants. Upon pulling it up we 

 will find slightly sunken areas on the stem just above 

 ground. The root system is generally destroyed, 

 with the exception of a small stub. 



The Organism. Fusarium viola was first de- 

 scribed by Wolf.* The sporodochia of the fungus 

 are borne within the stems. The macrospores are 

 hyaline, cycle shaped, 3-5 septate. The microco- 

 nidia are small, continuous; condiophorcs short. 



Control. The disease is likely to occur where 

 fresh barnyard manure is incorporated in the soil 

 before planting. Care should therefore be taken to 

 use only well rotted manure. Infected soils should 

 be steam sterilized, or disinfected with formalde- 

 hyde (see pp. 32-43). 



Wallflower (CheiraniTius cheiri) 



Cultural Considerations. Wall flowers require a 

 cool house, with a night temperature not higher than 

 45 to 50 degrees F. They thrive best when sup- 

 plied with an abundance of water and ventilation. 



Fimgi recorded on the wallflower. The wallflower 

 is considered a very hardy flower, and is easily forced. 

 The following fimgi recorded on this host may 

 prove serious : 



Cercospora cheirantM Sacc, Feronospora para- 

 sitica (Pers.) De. By. 



•Wolf, F. A., Mycologia 11: ig-aa, 1910. 



