PREFACE. IX 



stalks to blanch and become crisp, and 

 attain as great a length as possible. So 

 we transplant it when a few inches high, 

 and when the stalks have grown awhile 

 we surround them with earth. The plant 

 thus hemmed in, and having no access to 

 the sunlight except at the top, pushes 

 upward, as a man confined in a narrow 

 tube would struggle upward to get free, 

 and the juices not being acted upon by 

 sunlight, the chlorophyll, or green color- 

 ing matter, is not elaborated, and the 

 stalks grow white. Does any one suppose 

 that when a plant is thus surrounded with 

 earth it is as little liable to disease, as 

 when exposed to the air in its natural 

 state ? The stalk is composed of a fragile 

 cellular structure which abounds with 



watery juice, in which, besides other in- 

 2 



