xiv PREFACE 



man beings. We shall here endeavor to 

 show that although bad weather, over- 

 feeding, etc., may be important factors, 

 they are not the fundamental reasons for 

 failure. We shall study the specific causes 

 that lead to the diseases of the sweet pea; 

 the definite parasitic forms of life such 

 as insects, fungi, and bacteria that live 

 upon this plant and bring about its de- 

 struction. The nature of the attacking 

 insects is still incompletely known and 

 there is urgent need of further investiga- 

 tion of them. Of the fungi, nine produce 

 serious diseases in either roots, stems, foli- 

 age, or blossoms of sweet peas. Only one 

 bacterial trouble, however, is so far known 

 to affect sweet peas, and that is the dreaded 

 "Streak." To these troubles may be added 

 eel worm, red spider, and mites, all of 

 which add considerably to the losses. 

 In the discussion which is to follow, 



