HOWARD AND HOWARD. I I 



It will be seen that the F, cultures could be divided into the 

 following classes : — 



1. Cultures uniformly and densely felted derived from S S L L. 



2. Cultures uniformly and lightly felted derived from s s L L 

 and S S 1 1. 



3. Cultures with all plants felted, but not uniformly, derived 

 from S S L 1 and S s L L. 



4. Cultures with felted and smooth plants in the ratio 15 : 1 

 derived from S s L 1. 



5. Cultures with felted and smooth plants in the ratio 3 : 1 

 derived from S s 1 1 and s s L 1. 



6. Cultures all smooth. 



In dealing with the offspring obtained in the F 3 generation 

 from the various F._, plants, it was an easy matter to separate classes 

 4, 5 and 6 from the others and from each other. It was also com- 

 paratively simple to separate classes 1, 2 and 3 from each other by 

 the aid of the microscope. By examining a large number of plants 

 in each culture it was not difficult to see whether the felting was 

 uniform or not, and whether one or both kinds of hairs were 

 present. The distinction between the two constituents of class 

 3, namely, the cultures derived from plants of the gametic consti- 

 tution S s L L and S S L 1 was not quite so simple. As was shown 

 on page 9 plants of the constitution S s L L give in the F 3 S S L L 

 + 2SsLL + ss L L (long hairs completely developed), while 

 S S L 1 gives SSLL + 2SS L1 + SS11 (short hairs completely 

 developed). The best means of distinguishing these lies in the 

 well marked difference between plants represented by s s L L and 

 S S 1 1. Glumes with the long hairs only and complete are easily 

 distinguished under the microscope from those possessing the short 

 hairs only, both by the length and also by the density of the hairs 

 (the long hairs are more sparsely distributed than the short). On 

 this rests the separation of the constituents not only in class 3 

 but also in class 5. Had the two kinds of hairs been more alike, 

 these classes could not have been subdivided. 



It will be seen on examining the tables of the F 3 generation of 

 this cross that the determination of the various classes of felting 



