TRICHOMES OF OENOTHERA HYBRIDS AND PARENTAL LINES. 



11 



A study of the range of variation of the pear-shaped trichomes shows 

 that those of the hybrid in nearly every instance are less variable than 

 those of either parent. The equations in table 4, which are numbers based 

 on the extreme lengths of the trichomes, present the relative variability in 

 a graphic manner. 



TABLE 4. Comparative variability of pear-shaped trichomes of the Oenotheras. 



The distribution of the trichomes shows the influence of both parents in 

 an unequal degree. The awn- shaped trichomes are found on all areas, 

 /. e., on leaf, stem, and capsule, but the club-shaped and pear-shaped tri- 

 chomes are variously distributed. The former occurs on all of the areas 

 in Oenothera lamarckiana, but only on the capsule in Oenothera cruciata and 

 the hybrid. The distribution of the pear-shaped trichomes is much more 

 general and uniform; they occur on the leaf and the stem in parents and 

 the hybrids, and on the capsule in Oenothera cruciata, but are not present on 

 the capsule in the cross, and only sparingly so on the capsule in Oenothera 

 lamarckiana. Where there are several kinds of trichomes present the 

 distribution of each kind in parents and hybrid offspring must be com- 

 pared in order to derive any exact knowledge of the influence of the parents 

 or the behavior of the pubescent covering throughout the generations of 

 hybrids studied. It is doubtful whether the quality of hairiness in plants 

 can rightly be considered a "unit-character," and the analysis must be 

 carried yet further. 



