32 MISSISSIPPI EXPERIMENT STATION. 



Tabacum x N. sylvestris hybrid the pistillate parent, N. Tabacum, was 

 dominant over the shape of the leaves, while in the N. Tabacum x N. 

 alata hybrid, the staminate parent, N. alata, was dominant over the 

 same character. In the case of the majority of the characters of these 

 two hybrids, one parent was dominant in one cross, and the other parent 

 dominant over the same characters in the other cross. 



In most of the tissue of the N. Tabacum x N. alata hybrid, the 

 cells are ccnsiderably smaller than corresponding cells of either parent. 

 This, in part at least, accounts for the dwarfness of the hybrid. 



Brassica oleracca, var. caalo-rapa, Raphanus sativos and Hybrid. 



The Raphanus sativus used as a pistillate parent in the Raphanus 

 sativus X Brassica oleracea, var. caulo-rapa cross is a common radish 

 of vegetable gardens, — a variety with a large, white conical root. The 

 seeds of this plant germinate soon after planting and a large flowering 

 plant is produced in a few weeks. Figure 33 shows one of the plants 

 after it has been flowering for a short time. After beginning, the plant 

 continues to blossom throughout the remainder of the season. 



The Brassica oleracea, var. caulo-rapa used as a staminate parent 

 in the above cross, is a common purple variety of Kohlrabi of vegetable 

 gardens. Seed gathered from the staminate parent of the hybrid were 

 planted the first of June. They germinated at once, but the plants 

 grew rather slowly. No flowering stalks had started to form by the 

 first of October, when the plants were brought into the green-house. 

 In the green-house the plants grew slowly, and began to send out flower- 

 ing stems about the first of January; flower buds were first noticed 

 February 8. Figure 34 shows a plant soon after beginning to blossom. 

 (Further details of description of both kohlrabi and radish plants are 

 given in the tables and under the discussion of the hybrid.) 



The seeds produced by crossing radish and kohlrabi were planted 

 about May 15, 1909. They germinated at once, and produced two 

 seedling plants which at first resembled the radish parent considerably, 

 except in color; they had the purplish blue color of the male parent, 

 kohlrabi, the color not being so deep, however. 



One of the seedlings grew much more rapidly than the other, but 

 the two had the same general appearance at different stages. On Aug- 

 ust 1, the larger one of the two was 30 c. high, and had a spread of leaves 

 of about 70 cm. The leaves were at first ascending, but later became 

 spreading. At that time, the stem at the point of insertion of the large 

 leaves had enlarged considerably, forming a sort of globular thicken- 

 ing about 4 cm. in diameter. The root, at this stage, had also thickened 

 considerably. 



On August 16, the first flower buds were noticed. About this time, 

 the upper part of the stem began to branch, and lengthen rapidly, form- 

 ing long, slender branches, bearing flower buds (fig. 35). The first 

 buds that formed, dropped off before reaching full size; later ones devel- 

 oped farther and farther until some nearly perfect flowers appeared, 

 flowers with sepals; full size spreading petals, six stamens and a weU 

 formed pistil (fig. 41c.). However, the majority of the flowers failed 

 to open and had small and imperfectly developed parts. No good 



