564 THE STRUCTURE OF ECONOMIC PLANTS 



the remainder of the suspensor from cell d. Thus, following the 

 formation of the linear series of cells of the four-celled embryo, 

 the cells a, b, c, and d divide to form tiers of cells from which the 

 parts of the embryo are differentiated as noted above. (Fig. X95, 

 D, E, F.) Smith observed ii-celled embryos after 130 hours, and 

 the development of the histogens (dermatogen, periblem, and 

 plerome) occurred after 114 hours. The formation of the coty- 

 ledons takes place in about 18 days and the primary root shows a 

 definite histogenic organization at that time. (Fig. 7.^^, H.) 



The development of the endosperm precedes that of the embryo, 

 and the division of the primary endosperm nucleus begins in 

 advance of that of the zygote so that there may be an endosperm 

 of 8 or more cells before the two-celled embryo is formed. Between 

 94 and 130 hours after pollination, there are definite walls formed 

 in the endosperm; and at the end of 190 hours, it completely fills 

 the embryo sac surrounding the young embryo. (Fig. X95,G.) In 

 some cases, the adaxial faces of the cotyledons are closely appressed, 

 forming a single coil (Fig. 198, A), while in others they are curved 

 away from each other. (Fig. i^-y, A.^ 



The Fruit. — The fruit is a large berry which is globular or 

 oblate in the principal commercial varieties, but may be elongated 

 or pear-shaped in some of the special types. The very small cherry 

 tomatoes sometimes weigh but a fraction of an ounce, while the 

 table and market varieties weigh from 4!-^ to 6 or 7 ounces, and 

 some of the largest canning types, especially the Santa Clara, may 

 attain a weight of 9 to ix ounces. (Fig. X96.) As seen in transec- 

 tion, the fruit has from two to twenty or twenty-five locules, the 

 smaller numbers occurring in small-fruited forms and in the wild 

 types from which the cultivated varieties have been derived. The 

 principal commercial varieties have five to nine locules, except for 

 the large canning types which have the maximum number indi- 

 cated. 



The quality of the fruit is dependent upon color, flavor, shape; 

 and, structurally, upon the relative amount of outer and inner 

 wall tissue. MacGillivray and Ford (13) divided the tomato into 

 five fractions (outer and inner wall, inner locule tissue, gelatinous 

 pulp, skin, and seed) and computed the percentage composition of 

 each in order to determine their relation to quality. On this 

 basis, they concluded that "the outer and inner wall region of a 

 tomato fruit is the most valuable in producing tomatoes of high 



