1922] Setchell-Goodspeed-Clausen: Nicotiana Tahaciim 485 



class approximating type 10. Within the stenophylla class there 

 was a variation in the amount of "wing" on the petiole and in the 

 type of blade base, some having the abrupt base of type 1, whereas 

 others had an attenuated type of blade which gradually drew in to 

 the petiole. In the auriculata class there was also a variation from 

 the strict form of type 10 to a type which lacked the flaring auricle 

 typical for that form, and had a very short naked petiole. In addition 

 to this variation in the amount of "wing" of the constricted class 

 there was also a difference in the presence or absence of attenuation 

 noted for the stenophylla class, some plants having leaves abruptly 

 drawn in to the midrib, whereas others were very markedly attenu- 

 ated. The difference in this respect appeared to be equivalent in the 

 two distinct classes, i.e., it was independent of any difference in the 

 ' ' petioled " or " constricted ' ' condition. With respect to stenophylla 

 vs. AURICULATA the Segregation was 66 stenophylla : 32 auriculata. 



I7F3II2P17P8 was a sowing from I6F0II0P17P8, another steno- 

 phylla selection. The leaf classes obtained here were two, steno- 

 phylla (type 1) and sessilifollv (type 15). The segregation into 

 the two classes was distinct, but, as in other populations, there was a 

 great deal of variability in each class. There was attenuation of the 

 kind previously noted in both classes. Some of the petioled individuals 

 had distinct wings, but the larger number were naked. Some few 

 individuals had very short petioles. The segregation ratio was 76 

 stenophylla : 24 sessilifolia. 



ITF.H^Pi^PiQ was a sowing from 16F„H2Pi7Pin, a stenophylla 

 selection. The population was remarkably uniform in leaf shape, 

 which closely approximated angustif olia with minor differences. The 

 straplike leaves which are a characteristic feature of the upper por- 

 tions of plants of angustifolia were lacking in this population, and 

 the leaf tip and distal portion of the leaf blade did not narrow so 

 gradually in this population as in angustifolia. Otherwise, the char- 

 ^ acters of the plants throughout were closely similar to angustifolia: 



I7F3H2P17P22 was a sowing of seed of I6F2H2P17P02, a stenophylla 

 selection. Of the six F^j populations studied, this one exhibited the 

 greatest diversity in segregation. With respect to leaf base characters, 

 there were two outstanding classes, stenophylla and sessilifolia (type 

 15), which could be separated readily. Within the stenophylla class, 

 however, most of the individuals exhibited a more or less winged con- 

 dition. Within the sessilifolia class, on the other hand, most of the 

 individuals exhibited more or less narrowing of the leaf ba.se, like 



