APIUM GRAVEOLENS 453 



nia, and Florida. The several varieties are classed as self-blanch- 

 ing, and green or winter types; and in the former group, Golden 

 Self7Blanching represents about one-half of the total crop according 

 to Jones and Rosa (11). A form known as celeriac, A. graveolens, 

 var. rapaceum, D. C., is grown to a limited extent. In this type, 

 i to 4 inches of the fleshy root is edible. 



The celery plant, like the parsnip, is normally a biennial, al- 

 though under certain conditions it develops as an annual. In the 

 course of the usual biennial cycle, a well-developed root system, 

 a short crown stem, and a rosette of leaves are produced the first 

 year. (Fig. 119.) The second year, the much branched stems or 

 seed stalks elongate, producing a shrubby plant i to 3 feet in height. 

 (Fig. 2.30.) These bear compound umbels of small white flowers 

 which produce flattened fruits toward the end of the second season. 



A common practice in growing celery is to plant the seed in beds 

 from which the seedlings are transplanted three to four months 

 later; and, at the end of the first season, the crop is ready for mar- 

 keting. Occasionally, premature seeding occurs and the plant 

 develops flowers and fruits during the first season. There is con- 

 siderable variation in this regard, and in general, the vigorously 

 growing early varieties are most likely to go to seed the first season. 

 Thompson (15) has pointed out that "the environment seems to 

 control the expression of the hereditary factor or factors for annual 

 flowering and for seed." The environmental factors which may 

 inhibit seed stalk development are those which involve any serious 

 check in growth. These include freezing, stunting of plants by 

 overcrowding in the transplanting flats, and water deficiency. 

 High temperature, 70° F. or above, tends to prevent premature 

 seeding unless the seed stalks have already started prior to being 

 subjected to this temperature. On the other hand, plants sub- 

 jected to relatively low temperatures, 40° to 50° F., for two weeks 

 or longer are likely to seed prematurely, and this may occur when 

 plants are hardened in a cold frame in early spring. 



GENERAL MORPHOLOGY 



The Root. — The primary root system, consisting of a tap root 

 and its laterals, becomes very well developed in regions where 

 the plants are grown from seed sown in the open ground. When 

 transplanting is practiced, the tap root is destroyed and the fibrous 

 system is comprised of a large number of adventitious roots that 



