20 MISSISSIPPI EXPERIMENT STATION. 



From the above discussion and tables, it will be seen that the 

 pistillate parent influenced the external characters of the hybrid to 

 the extent of 64.6%, and the internal or microscopic characters 61.9%. 

 The staminate parent had influence to the extent of 35.4% and 38.1% 

 respectively. 



Among the external characters, there were only two_ over which 

 the pistUlate parent had pure dominance, while the staminate parent 

 did not have complete dominance over any. Of the ninteen characters 

 compared, seventeen were intermediate. Among the microscopical 

 characters, the pistillate parent had pure dominance over four, and the 

 staminate parent over one; sixteen of the twenty-one characters com- 

 pared, were intermediate. 



In these plants it seems that there is a close relationship between 

 external and internal characters, the parent having the most influence 

 over one, has a correspondingly greater influence over the other. The 

 extra size of the hybrid is produced by the largeness of its cells over the 

 corresponding cells of its parents (see table of microscopical characters), 

 rather than by a raultiplication of cells. 



Nicotiana Tabacam, N. alata and Hybrid. 



EXTERNAL CHARACTERS. 



Nicotiana Tabacum and N. alata were referred to in the preceding 

 pages. The hybrid, N. Tabacum x N. alata, is a slender, dwarfed 

 plant (fig. 8), height 40 cm., leaves few; linear-lanceolate, undulate, 

 sessile, 10 cm. long, 2.5 cm. wide; stem straight, cylindrical, 1.5 cm. 

 thick; flowers sparse in 3 or 4 terminal racemes; gamosepalous, tube 

 10 mm. long, 10 nerved, 5 teeth, linear subulate, 12 - 14 mm. long, 

 spreading at tip; corolla gamopetalous, salverform, tube 6.5 cm. long, 

 enlarged abruptly a few millimeters below the spreading lobes; lobes 

 regular, somewhat orbictdar with a short acuminate tip ; spread of lobes 

 4.2 cm. ; corolla, light pink in color, with green veins on outside; stamens 

 five, attached to the corolla tube toward the base, four as long as the 

 pistU, and one shorter; anthers brownish purple, 3.5 mm. long, 2 mm. 

 wide; filaments fUiform without thickening in the middle as in N. alata; 

 style 6 mm. long, filiform, stigma capitate, 2 lobed, ovary conical. 

 No fruit set, ovaries falling soon after the blossoms closed. PoUen 

 scarce, and grains nearly all shriveled and defective (fig. 4c). 



The hybrid a,bove described was a dwarf in comparison with its 

 parents, being smaller than either. It possessed certain characters 

 of each parent, but resembled the staminate parent in the main. The 

 form of the stem and branches was intermediate, — the main stem not 

 being so pronounced as in N. Tabacum, but more so than in N. alata, 

 while the lateral branches were smaller and fewer than in N. alata. 

 The leaves were very small; smaller than the leaves on either parent, 

 but they had a shape much like N. alata leaves. The flowers were inter- 

 mediate in size, shape and color. 



