Geranium Diseases 263 



is also a tendency to form large spots between the 

 principal veins. In this case, however, infection be- 

 gins at the margin of the leaf and progresses in- 

 wards. Spotted leaves may also become pale and 

 drop off prematurely. 



The Organism. Fseudomonas erodii is a short 

 but rather plump rod with rounded ends, borne 

 singly or in short chains of 2 to 3, active by means 

 of polar flagella. It produces no spores, and lique- 

 fies gelatin. 



Control. There seems no evidence that insects 

 are in any way associated with the spread of the 

 disease in the greenhouse. The causal organism 

 lives in the soil and is spread about by the splashing 

 of water during watering. By the removal of the 

 diseased parts and by careful attention to the water- 

 ing, the disease may be kept in check. The same 

 disease also attacks the wild geranium, Erodium 

 Texanum, which in this case may act as a carrier of 

 the causal organism. This weed therefore should 

 not be tolerated around greenhouses where gerani- 

 ums are grown, nor should it be used in the compost 

 soil. 



Soft Rot 



Caused by Bacillus caulivorus Pr. and Del. 



Symptoms. This disease was found by Gallo- 

 way * to be destructive to greenhouse geraniums. 

 It attacks the stems which at first become soft and 

 mushy and later turn black and shrivel (fig. 56, c). 



*GaIloway, B. T., Jour. Mycol. 6; 114-115, 1890. 



