Ornamental Plaiits 429 



greenish-black, flat sclerotia, 1-13^ mm. in diameter, are 

 formed in the stems. 



Dead leaf and stem remains should be removed from the 

 peonies before they are set in the ground. Bordeaux mix- 

 ture may be used after the plants appear in the spring. 

 Infested beds should be steamed. Drop (Sclerotinia) . See 

 lettuce. 



PETUNIA 



Drop (Sclerotinia) . See lettuce. 



PHLOX 



Powdery-mildew (Erysiphe cichoracearum DC). — This is 

 of general distribution and injurious. Leaf-spot (Cercospora 

 phlogina Pk.). — Brown circular spots occur on the leaves. 



PINK 



Rust (Puccinia arenarice (Schm.) Schr.). — This rust was 

 described in 1803 by Schumacher. It is quite common upon 

 various members of the pink family, for example, chick- 

 weeds, corn cockle, Bouncing Bet, etc. The sori are large, 

 raised blisters arranged in characteristic concentric circles. 



Diseased plants should be burned. 



PRIMROSE 



Leaf-spot (Phyllostida primulicola Desm.). — Large, cir- 

 cular, brown, dead spots are produced upon the leaves. 

 Minute dark pycnidia may be seen. Leaf-spot (Ascochyta 

 primulce Trail). — Well-defined oval spots, resembling those 

 of the phyllosticta leaf-spot, are formed. These two diseases 

 cannot be distinguished without the aid of the microscope. 

 Leaf-spot (Ramularia primula; Thuem.). — In this disease 

 the blotches are yellow with centers of ashen whiteness. No 

 pycnidia are present, but instead a gray coating of mold. 

 Anthracnose (Colletotrichum primulw Hal.). — In this blight 



