382 ELEMENTARY STUDIES IN BOTANY 



deep is marked in the fine soil, the seeds are dropped in 

 (twenty-five to fifty in a foot), and then covered with fine 

 and pressed-down soil. In fifteen to twenty days the plants 

 are thinned out, leaving eight to ten in a foot ; and at the 

 same time a second row is planted. About twenty days later 

 the first row is thinned again, so that the plants are six to 

 twelve inches apart (according to size) ; the second now re- 

 ceives its first thinning ; and a third row is started. Even 

 a fourth row may be started, but it is not likely to do very 

 well on account of the hot weather. 



For market purposes, the plants are started in the green- 

 house in February, and planted out of doors as soon as the 

 weather will permit. A large industry has developed, also, 

 in forcing lettuce under glass at all times of the year, so that 

 fresh lettuce can always be obtained. 



88. Celery. Celery is cultivated for the leaf stalks 

 (petioles), which are blanched and made tender. It is 

 poorly grown if it is greenish and tough. Celery belongs to 

 the parsley family (Umbelliferse) , and its well-known asso- 

 ciates were enumerated in connection with the account of 

 parsnips and carrots (p. 376). 



This vegetable is in such extensive use and requires such 

 special treatment that it has come to be cultivated as a field 

 crop rather than as a home garden crop. For its best develop- 

 ment it requires a special soil, really a bog soil, but it can 

 be grown well on clay or even sandy soils if they are enriched 

 and irrigated. Although this is a market garden crop rather 

 than a home garden crop, the use of celery is so universal that 

 some information as to its culture seems desirable. 



The seeds are sown in special frames of various kinds, and 

 germination is a slow process, the seedlings being ready to 

 transplant in about three months. For the early crop in the 

 northern states, therefore, the seeds are started in January; 

 and for the late crop they are started in March. The seeds 

 are broadcast, and the young seedlings are transplanted to 



