LYCOPERSICUM ESCULENTUM 557 



that the separation surface of the detached portion of the pedicel 

 may be convex, while that of the remaining part of the pedicel is 

 slightly concave. 



The separation of the adjacent cells results from a dissolution of 

 the middle lamellae, and on the basis of Kendall's experiments, it 

 seems probable that turgor is not an initiating factor, but serves 

 mechanically to hasten the process. It appears from this work 

 that the middle lamellae of the cell walls in the abscission zone are 

 more easily hydrolyzed than are those in the more distal portions, 

 and the agent of hydrolysis is thought to be an enzyme. No cell 

 divisions or elongations were observed accompanying the process 

 of abscission. 



In addition to this type of true abscission, individual plants may 

 lose their flowers by a process which involves no active cell separa- 

 tion. In such cases, the flower merely wilts and dries back to the 

 abscission groove, where it may hang until broken off by some 

 mechanical means. When this type of abscission occurs, it is first 

 indicated by a loss of chlorophyll in the pedicel, beginning at the 

 tip and extending to the separation zone. In many instances, both 

 types of abscission may occur in the same plant. 



The Flower. — The pendent yellow flowers are perfect, hypog- 

 ynous, and regular; but in cultivated varieties, the number of 

 floral parts in each cycle is variable. The persistent calyx consists 

 of a very short tube terminated by five to ten lobes. The rotate 

 corolla also has a short tube which is expanded at the top into five 

 or more lobes that are at first greenish-yellow, becoming a brilliant 

 yellow later when the flower is fully developed and the lobes 

 reflexed. The five or more stamens are partially adnate or undi- 

 verged from the calyx tube. The filaments are short and the 

 connivant anthers are united laterally to form a hollow cone 

 around the pistil. The pistil consists of two to several carpels 

 and its elongated style and smooth, flattened stigma extend through 

 and somewhat beyond the encircling androecium. (Fig. 191, B.) 



The solanaceous plants are usually pentamerous and the basic 

 floral plan is 5-5 -5-i. Warner (35) has described the ontogeny of 

 a flower of this type, while Cooper (7} and Smith Qirf) have pub- 

 lished accounts of the development of the hexamerous form which 

 is the most common floral plan in many commercial varieties. 

 (Fig. 191, C) In fact. Cooper found only one pentamerous blossom 

 in more than a thousand flowers examined. In addition to L. escu- 



