1912] Goodspeed: Nicotiana Hyhrids 89 



have been fully reported. Thus Clark (1904) worked upon the 

 value of seed-selection according to specific gravity and sum- 

 marizes the work, along this particular line, of previous investi- 

 gators— Haberlandt, Wollny (1885), Hellriegel (1883), and 

 others. Shamel (1904), Weber and Boykin (1907), Lill (1910), 

 Scherffius (1909), and many others have conducted investiga- 

 tions connected with the relation of weight, size and density to 

 germination and subsequent development of wheat, cotton-seed, 

 tobacco seed, etc. The general result of all this work has been 

 to establish the value for the agriculturist of careful seed-selec- 

 tion and especially the advantage of sowing heavy rather than 

 light seed for the subsequent production of uniformally vigorous 

 plants and thus of the most valuable crops. In agricultural 

 practice the plants grown from heavy tobacco seed have been 

 found to give often over 90 per cent germination and to produce 

 plants that grew more rapidly, matured earlier and were best 

 developed and most vigorous; while from light seed "small, 

 irregular and undesirable" plants develop (Shamel, 1904, p. 440; 

 cf. Waldron, 1910, and Love, 1910, p. 423). These conclusions 

 are based upon the separation of well-known commercial strains 

 of tobacco and give no results directly applicable to the investi- 

 gation in hand. 



II. DESCRIPTION OF EXPERIMENTAL MATERIAL 



Distinguishing Characteristics of Parents and Appearance 



OF Hybrids in F^ 



The experimental material consisted of the second hybrid 

 generation seed produced by self-fertilizing the flowers of one 

 Fj hybrid plant, representing the cross Nicotiana Tadacum var. 

 macrophylla ^y^ Nicotiana Tabacum var. virginica (^. Nicotiana 



22 



Tabacum var. macrophylla is U. C. B. G. 07 (Setchell, 1912, 

 p. 8, plate 6) ; the original seed was received under the name 

 quoted from Professor 0. Comes. Nicotiana Tabacum var. vir- 



78 



gi7iica is U. C. B. G. 05 (Setchell, 1912, p. 6, plate 3), a form of 

 N. Tab. var. virginica. Comes (1899), but is better referred to 

 under the trade name of Marijland, under which name the 



