DISTINCTIONS IN CULTIVATED BARLEYS. 23 



FERTILITY. 



The variation in fertility is the most evident and the most vital of 

 all the modifications that occur in barley. At each node of the 

 rachis a group of three single-flowered spikelets is produced. In 

 the 6-rowed barleys, each of these develops a separate kernel. As 

 the groups of spikelets are placed alternately on opposite sides of 

 the rachis the result is six columns of kernels from the base to the 

 tip of the spike. . In the 2-rowed barleys, only the central spikelet 

 at each node is fertile, and therefore there are but two columns of 

 grains. This reduction does not take place by the elimination of 

 the outer spikelets but by their sterility. The median floret of each 

 set of three accomplishes its normal development, while on either 

 side are the small, undeveloped, infertile florets. However, the 

 sexual organs have not disappeared. The three stamens reach an 

 appreciable size and the ovary, though rudimentary in some ways, 

 persists even to the plumose stigma. In one group of the 2-rowed 

 barlei^s there is a still further modification of the lateral florets. In 

 Abyssinian barleys there is a considerable number of forms in which 

 the lateral spikelets are rudimentary ; that is, they no longer contain 

 even infertile flowers, the whole spikelet being reduced to structures 

 that are little more than hairlike. 



In the experience of the writer these well-known taxonomic divi- 

 sions have proved entirely stable. The observations have included 

 hundreds of varieties, and these varieties have been grown under 

 such varying conditions as to stimulate monstrous developments in 

 many structures, but in no case has there been indication of bridging 

 over these separations. It is the opinion of the writer that the numer- 

 ous instances of exceptions recorded have been misinterpreted. The 

 one cited by Kornicke (15) was most probably a cross, as the varia- 

 tion of 'the progeny was such as is always secured by hybridization. 

 The more common exceptions usually described are the occurrence of 

 3-rowed and 8-rowed freaks, and 2-rowed barleys in which some of 

 the lateral florets are fertile. All three exceptions are probably due 

 to the formation of adventitious spikelets. Such spikelets are com- 

 mon, and if several of them occur along one side of the rachis of a 2' 

 rowed barley the result is a 3-rowed spike. If a duplication of the 

 groups of spikelets at the nodes of one side of the rachis occurs in a 

 6-rowed barley, the result is nine rows, which, if imperfect in any 

 way, are easily mistaken for eight. It is entirely possible that florets 

 of lateral spikelets of 2-rowed varieties are sometimes fertile, but in 

 practically all of the numerous cases that have been noted by the 

 writer a close inspection of such grains has shown them to be adven- 

 titious, with the sterile floret also present. 



