72 DISEASES OF GLASSHOUSE PLANTS 
accompanied by imperfect circulation of the air and 
injudicious watering, are favourable to the disease. For 
a description of the fungus and method of control, 
see page 64. 
Fusarium and Penicillium Rots.—Certain species of 
Fusarium and the common blue mould Penicilliwm produce 
a bulb rot of the hyacinth, narcissus, and tulip. The 
rot commences from the base of the bulb, and is typically 
a storage rot. Unsuitable conditions at the time of 
harvesting and imperfect drying of the bulbs are the 
main factors connected with 
the disease. Diseased bulbs 
are frequently planted be- 
cause external signs of rot are 
absent. The disease organ- 
isms attack the base of the 
bulb and work up into the 
centre, where the flowering 
shoot may be destroyed. 
Such bulbs rarely flower, 
si 
§ “— no new bulb is formed, and 
the old one is converted into 
a powdery mass. 
Fig. 13. Botrytis disease of the tulip : Attention to the condi- 
(a) bulb showing black sclerotia, . ° . 
(o) fungal growth on the bulb. tions operative at harvesting 
and during storage so as to ensure that the bulbs are 
perfectly dry, and the elimination of rotten bulbs from 
which infection may spread, are the best ways of 
preventing the disease. 
