Sweet Pea Diseases 339 



symptoms of streak are here given to enable the 

 grower to know the disease should it ever appear in 

 the greenhouse. Like the Bacteriosis of beans, streak 

 makes its appearance in wet houses. On the sweet 

 pea the disease usually appears just as the plants 

 begin to blossom. It is manifested by light reddish- 

 brown to dark brown spots and streaks (the older 

 almost purple) along the stems, having their origin 

 usually near the ground, indicating the fact that the 

 distribution of the disease is by the spattering of 

 water droplets and soil particles, and that infection 

 takes place through the stomata. The disease be- 

 comes quickly distributed over the more mature 

 stems until the cambium and deeper tissues are de- 

 stroyed in continuous areas, whereupon the plant 

 dies. Occasionally petioles and leaves show infec- 

 tion; the latter exhibiting the usual water-soaked 

 spots and resembling the bacterial leaf blight of 

 beans. 



The disease is not a vascular infection ; it confines 

 its attacks to the mesophyll, the cambium and deeper 

 parenchymatous tissues. The lesions of the stems 

 gradually enlarge and deepen until they come to- 

 gether. 



Downy Mildew 



Caused by Peronospora trifoliorum De By. 



Symptoms, This trouble usually makes its ap- 

 pearance when the plants are a few inches high or 

 it may attack older plants. Affected leaflets become 



