LYCOPERSICUM ESCULENTUM 555 



The number of flowers comprising an inflorescence may vary 

 from four to twelve or more. Bos well and his coworkers (4) found 

 that the more important commercial varieties bear an average of 

 four to five flowers per cluster; and that, under conditions where 

 the plants are not pruned or staked, from two to four flowers set 

 fruit. Ordinarily, it is unusual for more than two flowers of an 

 inflorescence to be open at one time; and, because of this pro- 

 gressive development, a single raceme may have small fruits, open 

 flowers, and buds. Under greenhouse conditions, some unproduc- 

 tive flowers occur. These may be classified into three categories: 

 (i) those producing small fruits that ripen prematurely before 

 attaining a marketable size; Ql) those having a persistent calyx, 

 but in which the fruit does not develop; and (3) flowers that 

 absciss. 



Floral Abscission. — Kendall (17) has described the histology 

 of the pedicel of the flower and fruit with reference to the develop- 

 ment of the separation zone, the process of abscission, the time 

 involved, and experimental methods of inducing abscission. The 

 zone of separation in Lycopersicum is located at a mid-point in the 

 pedicel in contrast to Nicotiana where it occurs at the base. It is 

 externally visible because of enlargement at that point and owing 

 to the development of a circumferential groove which is fully half 

 the depth of the cortex. (Fig. 1.^1., A, and Fig. ^^t,, A.') 



The vascular system of the pedicel forms a cylinder of separate 

 bundles which are surrounded by parenchyma. Outside the funda- 

 mental parenchyma, there is a layer of collenchymatous cells in 

 that portion of the pedicel which is proximal to the groove, but 

 this does not develop in the portion distal to it. Between the 

 collenchyma and the epidermis there is a zone of chlorenchyma. 

 (Fig. 193, B.) The separation layer consists of from three to six 

 tiers of cells which are located in the plane of the groove. In 

 buds in which the calyx is less than 1. mm. long, the groove is not 

 detectable, but it begins to appear when the corolla is about i mm. 

 in length, and is well developed in young buds in which the corolla 

 does not exceed 3 mm. The cells of the separation zone are smaller 

 than those on either side of it, and this difference in size becomes 

 more noticeable as the flowers mature, since the cells of this region 

 do not enlarge as the adjacent cortical cells increase in size. There 

 are apparently few cell divisions in the separation zone, but the 

 cells do retain their meristematic potentialities. The mechanical 



