Nov. 19. 1921 Ash Content of Awn, Rachis, and Palea 439 



ASH IN THE RACHIS 



The deposit of ash in the rachis of the barley spike is less easily inter- 

 preted than is the ash in the awns. The awns serve as a place of de- 

 posit, probably for ash excluded from the cell sap. The rachis, on the 

 other hand, is a conductive organ through which passes the nourish- 

 ment of the various kernels and the water which is transpired from the 

 awns. The daily deposit of ash in the rachis is confusing. Although 

 a large number of analyses were made they are not reported, as no 

 plausible explanation could be offered for the fluctuations. The gen- 

 eral trend of the results is indicated in figure 2. 



In 191 7, in plot 8, which received no irrigation after flowering, the 

 ash gradually increased from about 2 per cent at flowering time to 

 about 7 per cent at maturity. In this case there were no large fluctua- 

 tions. Where irrigation water was applied, the ash content was con- 

 siderably increased. Although this increase was exhibited on all plots, 

 in many cases the increases were irregular, fluctuating and not easily 

 explained. The results in 19 16 were more uniform and showed a gradual 

 increase from flowering to maturity, the content reaching 11 to 14 per 

 cent at that time. In 191 7, on the irrigated plots, the content at ma- 

 turity ranged from 12 to 18 per cent. 



While the drop in ash in plot i is doubtless exaggerated by the acci- 

 dent of sampling, most of the large fluctuations in the daily samples of 

 191 7 are not thought to be errors of determination. On the plots where 

 the water content was low the fluctuations either did not occur or were 

 small. The analyses of the awns and rachises were made from the 

 same samples at the same time and in the same way. Those of the awns 

 were satisfactory. It is probable that the variations in the ash of the 

 rachises were due to some relationship of soil water and the rate of 

 transpiration. 



In a previous paper ^ it was shown that the removal of the awns re- 

 sulted in an increase of the ash content in the rachis of an awned barley. 

 From this it was inferred that the rachises of awnless barleys were likely 

 to be high' in ash. It was known that awnless and hooded varieties 

 shattered badly in the field. It was to discover varietal differences, if 

 such existed, that the samples were taken which are reported in Table 

 III. As previously stated, the experiment included not only varieties 

 which differed in the character of the awns but in many other taxo- 

 nomic characters as well. It was found that the ash content varied 

 greatly with the variety. As these samples were grown in California, 

 the percentage of ash is higher than if the samples had been grown in 

 the more humid districts. In all determinations made on barleys grown 

 in Minnesota and at Arlington, Va., under humid conditions and where 



1 Hari,an, Harry V., and Anthony, Stephen, development OF barley kernels in normal and 



CLIPPED SPIKES AND THE LIMITATIONS OP AWNLESS AND HOODED VARIETIES. In JOUf. Agr. Research, 



V. 19, no. 9, p. 431-473, 13 fig. 1930. 



