viii 



Introduction 



ber of establishments and their money value have 

 lately increased by at least fifty per cent. This, 

 therefore, represents a vast sum of money and an 

 important industry of the United States which can- 

 not be ignored. 



Plants under greenhouse culture are far from 

 being subjected to normal conditions. The expres- 

 sion ''tender as a hothouse plant" well expresses 

 the truth. Because of this fact greenhouse plants 

 are naturally more susceptible to diseases indoors 

 than similar plants grown in the open. This at once 

 emphasizes the importance of studying the diseases 

 of greenhouse crops with a view to furnishing the 

 growers such information as may help them to re- 

 duce important plant diseases and thereby increase 

 their profits. We have as yet no available figures as 

 to the money losses from diseases of greenhouse 

 crops. A conservative estimate, however, may place 

 these losses at about thirty per cent. 



The literature on diseases of greenhouse crops in 

 the United States is rather fragmentary and scat- 

 tered. The American Plant Pathologists have been 

 too busy in devoting much time to the investigations 

 of the diseases of cereals, fruit and truck crops. 

 Considering that plant pathology is only a new sci- 

 ence, the diseases of the greenhouse crops had of ne- 

 cessity to be neglected. It is, therefore, the aim and 

 purpose of the present volume to bring together 

 available information on the subject and to place it 

 at the disposal of the greenhouse men. The author 

 realizes too well the incompleteness of this work; 



