Aug. 2, 1920 Daily Development of Kernels of Hannchen Barley 425 



grain, the results are much more uniform. In figure 15 is given the total 

 nitrogen per kernel in both 1916 and 1917. The curves are essentially 

 identical. The divergence after the seventeenth day is due to the lesser 

 gain in dry matter after that time in 191 7. The divergence in nitrogen 

 content is about the same as in the dry matter shown in figure 1 1 . The 

 results obtained agree very closely with those of Schjeming in Denmark 

 and Brenchley in England. 



INCREASE IN ASH 



The percentage of ash in the kernel decreases uniformly from flowering 

 to maturity. At the time of fertilization the percentage is high, and for 

 48 hours after flowering it is more than 7 per cent. The decrease in 

 percentage from that time is not due to loss of ash, as may be seen in 

 figure 16, but to the more rapid increase of other materials. In other 

 experiments, to be reported later, it has been found that the ash content 

 is in fairly close relation to the amount of water available for the use of 

 the plant. The curves of the ash content of 191 6 and 191 7 again indicate 

 that the irrigation of 1917 was insufficient. The greater growth of 191 6 

 has been mentioned previously; and while a part of it may have been 

 due to better soil in 191 6 a part was certainly due to the more generous 

 irrigation of that year, coupled with the fact that the soil used in 191 6 

 absorbed water somewhat more readily than that used in 1917. 



PERIODS OF DEVELOPMENT 



The Hannchen barley at Aberdeen exhibits a development which is 

 very uniform from year to year. This development, while steadily pro- 

 gressive from flowering to maturity, varies considerably in its nature. 

 The first five days after fertilization are marked by an extremely rapid 

 growth in length. The kernel has reached its maximum in this respect 

 by the seventh day. About the time the growth in length ceases the 

 rapid gain in dry matter begins and continues for about two weeks. 

 Thus the fifth or sixth day marks a change in the character of growth. 

 About the ninth or tenth day a sticky substance is formed in the outer 

 layers of the caryopsis, which causes the glumes to adhere thereafter to 

 the developing kernel. The nature of this substance has not been 

 included in this study, but its origin is evidently in the caryopsis and not 

 in the glumes. This has been demonstrated in the making of hybrids. 

 In this process the upper part of the florets is removed. At maturity 

 the tips of the projecting kernels are often found stuck fast to the paper 

 in which the spike was wrapped. The appearance of this adhesive sub- 

 stance on the ninth or tenth day would seem to mark a second stage of 

 development. Since the inner tissues -of the kernel are very soft, it is 

 difficult, from this time until the kernel has somewhat hardened, to 

 remove the glumes without tearing the kernel. This hardening occurs 

 183718°— 20 3 



