270 Diseases of Greenhouse Crops 



and emerge singly through its lateral walls. For 

 methods of control soil sterilization is recommended 

 (see pp. 32-43). 



Bulb Rot 



Caused by Rosellinia massinkii Sacc. 



This fungus is reported by Halsted * as thriving 

 on hyacinth bulbs. However, the nature of the in- 

 jury is not clearly stated by him. 



The Organism. The fungus produces dark brown, 

 elliptical spores. The asci are borne in globose or 

 depressed dark colored perithecia. 



SCLEROTINIA ROT 



Caused by Sclerotinia bulborum Rehn. 



Symptoms. The disease is first manifested as yel- 

 low stripes or blotches on the leaves and bulbs. With 

 the advance of the trouble, a velvety olive brown 

 mold is formed on the surface of the spots. This 

 growth is but the conidiophores and conidia of the 

 causal fungus. The black sclerotia are developed 

 on the rotted bulbs, and are found mostly within 

 the outer scales. As the sclerotia winter over, 

 they germinate by sending out slender stalks which 

 bear apothecia and ascospores. The Botrytis form 

 of spores is the most prevalent and is depended 

 upon by the fungus to spread it quickly from plant 

 to plant. 



* Halsted, B. D., N. J. Agr. Expt. Sta., Fourteenth Ann. Kept 

 393. 1893- 



