sept.i.i92o Fixed Intermediate, Hordeum intermedium haxtoni 589 



long awned and that there is no approach toward the homozygous inter- 

 mediate. The second variety, Summit, which for other reasons is 

 thought also to be of hybrid origin, produced spikes with infertile lateral 

 florets much more rarely. It is suggested that these barleys may be 

 forms of the 6- rowed segregate AAbbcc, homozygous for the absence of 

 the two secondary factors of fertility. 



POSITION OF FERTILE LATERAL SPIKELETS 



Aside from the question of the amount of fertility in the lateral florets, 

 the location of fertile florets on the spike is of interest. In the common 

 varieties of barley the largest kernels are produced about one-third of 

 the distance from the base of the spike to the tip, in both the central and 

 the lateral spikelets. The longest awns are attached to these florets, 

 and they exhibit a progressive decrease in length toward the tip of the 

 spike. The fertility of the homozygous intermediate runs in the reverse 

 order. When only a few kernels are produced they are found in the 

 upper third and gradually extend downward from the tip in the more 

 fertile intermediates. The most fertile lateral florets in the Mansfield 

 variety are found near the center of the spike. 



ABERRANT LINE NO. 2)7 



In Table I line No. 37 was found to diflfer greatly from the other 

 members of group 2 in both appearance and fertility. It is much lower 

 in fertility than the other individuals and, with the exception of one or 

 two florets, is similar in appearance to the fixed intermediate. This 

 plant is the only one of the 87 whose appearance is difficult to explain. 

 It is not believed that the hypothesis of its being homozygous for the 

 absence of the third factor is adequate explanation for its wide departure 

 from type. For this reason this line was excluded in the later discussion. 

 It is possible that the supposed Fj plant is the result of a natural hybrid. 

 The appearance of the forms in any class varies with the parents used. 

 Some combinations result in greater fertility in the various classes, 

 others result in much less. If the Fi kernel from which this Fj plant 

 developed had been fertilized by some neighboring 6-rowed variety less 

 vigorous than the Manchuria or by a low-fertility intermedium form, 

 such a plant as No. 37 might result. The opportunity for accidental 

 crossing in the F^ generation is unusually good. The lateral florets of 

 the Fj plants are much more likely to open at flowering time than are 

 the normal barley florets, and they flower after the spike is exserted. 

 The flowering glumes are less interlocked and open more readily and more 

 widely. The flowers are more frequently deficient in pollen, and those 

 not self-pollinated remain open for hours or even days, affording unusual 

 opportunity for cross pollination. 



