PREFACE xiii 



the first time they tried to grow sweet peas 

 because of total loss from disease. Others 

 who have grown them for years have been 

 meeting with difficulties that are consider- 

 ably reducing their profits. The layman, 

 particularly the housewife so proud of her 

 row of sweet peas by the house, has seen 

 many of them carried off by blights and 

 the remainder dry up and wither away. 



Naturally the blame fell at once on the 

 seedsman, who was accused of supplying 

 a poor grade of seed. In seeking justifica- 

 tion, seedsmen attributed the growers' 

 failures to bad weather, to drought, or to 

 the green aphids. A few seed catalogues 

 and some popular articles on the culture 

 of the sweet pea asserted that the plant is 

 unusually free from disease, and that all 

 failures are due to overfeeding. Many 

 practical men do not realize that plants 

 have diseases just as do animals and hu- 



