1922] Setchell-Goodspeed-Clausen: Nicotiana Tahacum 463 



the generations later than F^ were grown only from Ha and H^, the 

 larger number from H^. The predominance of H^ in the later families 

 selected for the continuation of the work was not, however, due to any 

 especially different behavior evidenced in that particular series. 



1. PARENTS OF THE ANGUSTIFOLIA-MACEOPHYLLA SERIES 



By selecting angustifoUa and niacrophylla for crossing, two varie- 

 ties were obtained which resemble each other in height and general 

 habit, but Avhich differ strikingly in leaf and flower characters. The 

 differences are sufficiently great to lead one to regard them as belong- 

 ing to different species ; in fact, all five Tabacum varieties selected by 

 us as possibly fundamental differ sufficiently among themselves to be 

 regarded as species in the Tahacum section rather than as varieties. 

 It is not our intention, however, to emphasize this point, since any 

 discussion would of necessity lead to a general survey of all the known 

 varieties and races at present included under Tahacum. If, however, 

 these five, viz., angustifoUa, macrophylla, "Cavala," Maryland, and 

 "Brazilian" (cf. Setchell, loc. cit.) could be considered by themselves 

 as wild plants, it seems to us that any taxonomist of the present day 

 would certainly award to each of them the rank of a separate species. 

 These considerations should be borne in mind in estimating the signifi- 

 cance of the results obtained through crossing. 



AngustifoUa, U. C. B. G. 68/07, is a variety which has long been 

 known and which is represented in our breeding experiments by a 

 pure line very closely approximating the type. It has been figured 

 and discussed by one of us (Setchell, loc. cit., p. 9, pi. 7). The photo- 

 graph given there is of a young plant just coming into flower and 

 consequently does not represent the habit of the plant in full blossom 

 or in fruit, after the full number of laterals is developed. A plant 

 in the height of its vigor is represented in plate 55, figure 1. In 

 stature angustifoUa belongs to the low corymbose group of Tahacum 

 varieties, which also includes the forms bred in the University of Cali- 

 fornia Botanical Garden under the names calycina and macrophylla, 

 and which is in decided contrast to the tall, more "racemose" (al- 

 though these may be "corymbose" at the top) forms such as alha and 

 virginica. 



In height angustifoUa varies from 75 to 120 cm. The central axis 

 develops its corymbose panicle of short racemes first, but it is usually 

 soon overtopped by the successive laterals developed basipetally, each 



