LYCOPERSICUM ESCULENTUM 561 



pedicel, receptacle, calyx, and style; and Makemson (14) found 

 stomata and lenticels on the ovary. 



MicROSPOROGENESis. — According to Smith (17) sporogenous 

 tissue develops early in the anthers, and a row of hypodermal 

 archesporial cells are differentiated in very young buds. Inside 

 the archesporial cells, a single row of primary sporogenous cells 

 is formed and these continue to divide. The outside row becomes 

 the outer tapetum; while, early in development, the vegetative 

 cells bordering the inner margin of the sporogenous tissue form 

 the inner tapetum. The tapetal cells are usually binucleate, 

 separating later as they undergo various form changes. In the 

 tomato, it appears to be typical that metaphases, anaphases, and 

 telophases of the second reduction division may occur simultane- 

 ously in a single locule. No wall formation takes place until both 

 nuclear divisions are completed. The microgametophytes are 

 binucleate, containing a generative and tube nucleus; and, follow- 

 ing pollination, the generative nucleus divides before the pollen 

 tube reaches the megagam^etophyte. 



Pollination. — Dehiscence of the stamens begins X4 to 48 hours 

 after the opening of the corolla. Each locule contains several 

 hundred pollen grains, and the anthers split longitudinally in an 

 introrse manner so that the pollen may fall directly on the stigmatic 

 surface of the pistil. Namakawa (x5) has investigated dehiscence 

 in several solanaceous plants including tomato; and, although 

 there is some variation in detail, the general mechanism is rela- 

 tively constant. The epidermis at the point of abscission is 

 underlaid by a special disjunctive tissue that is from one to seven 

 layers in thickness. Anthesis may occur in one of three ways: 

 by the solution of the middle lamella of the epidermal cells along 

 the line of dehiscence; by the solution of the entire wall of such 

 epidermal cells; or by mechanical rupture of the epidermis due 

 to hygroscopic action of a fibrous layer of cells in the anther 

 wall. 



The type of dehiscence, the pendent position of the flowers, and 

 the fact that the stigmas are receptive to pollen one or two days 

 before the anthers split, usually result in self-pollination. Some 

 crossing does occur, however, and as much as a 5 per cent cross- 

 pollination has been recorded in certain long-styled varieties in 

 which the style and stigma project beyond the staminal cone. 

 Where cross-pollination does occur, it is carried on through the 



