18 



BULLETIN 925, U. S. DEPARTMENT OF AGRICULTURE. 



in the number of rows on the upper ear, and in the length of the 

 ear stalk. The brachytic plants, on the other hand, exceed the 

 plants of normal stature in the number of branches in the tassel, 

 the diameter of the culm, the total number of leaves, and the number 

 of nodes that produce roots. The frequency distributions for the 

 total number of nodes for the Boone, brachytic, and first and second 

 generation hybrids are shown in figure 7. 



The reduced length of the branching axis of the tassel of the 

 brachytic plants clearly indicates that brachysm includes the termi- 

 nal inflorescence. Although the 

 length of the rachis from which 

 branches arise is reduced, the total 

 number of branches is increased. 

 This increase is comparable to the 

 increase in the number of nodes on 

 the culm, which is coincident with 

 reduced stature. 



The abortion of the terminal in- 

 florescence discussed on page 4 

 did not appear in the progeny of 

 the brachytic-Boone hybrid. As 

 the evidence available thus far for 

 this character indicates a Men- 

 delian behavior, it would seem that 

 the brachytic-Boone combination 

 will be free from this defect. 



It is an interesting fact that, 

 although the longest internodes on 

 brachytic plants are less than one- 

 third the length of the longest 

 internodes on normal plants, the 

 length of the longest leaf sheath is 

 not reduced on the brachytic plants, 

 nor is the position of the sheath 

 altered. 



There is a correlation of 0.434 ±0.047 between the length of the 

 leaf sheath and the length of the internode on normal plants,, indicat- 

 ing a definite tendency for the sheaths to cover the internodes. Curi- 

 ously enough, however, the longest leaf sheath does not inclose the 

 longest internode, but on the contrary is produced, on the average, 

 four internodes below the longest internode. That the correlation 

 is no closer than 0.434 is not surprising, since the length of internodes 

 on plants of normal stature is so largely determined by environ- 

 mental conditions and may be altered at a comparatively late date, 

 while the dimensions of the sheath are relatively constant. 



/7 19 21 23 2S 

 At UMBER NODES 



27 



Fig. 7. — Frequency distribution for to- 

 tal number of nodes in Boone, bra- 

 chytic, Boone X brachytic Fi.and the 

 normal and brachytic segregates in 

 the F 2 of brachytic X Boone. 



