448 



Journal of Agricultural Research 



Vol. XIX, No. 9 



normal spikes. The graphs of wet weights per kernel coincide essentially 

 until the fourteenth day after the experiment started. If there were a 

 mechanical injury it would probably most seriously affect the kernel 

 immediately after the injury. 



After the fourteenth day the kernels in the normal spikes increase 

 more rapidly in weight and size than do those in the clipped spikes. On 

 only two days after July 14 do the clipped spikes exceed the normal ones, 

 and these excesses are unquestionably due to the error of sampling which 

 comes from the use of a single spike for this purpose. 



The difference in rate of development begins to be noticeable about 

 the time that the growth in length is completed. This coincides roughly 

 with the beginning of the period of rapid starch infiltration. Whether 



/r/y. 



Fig. I. — Graph showing growth iu length, lateral diameter, and dorsoveutral diameter of kernels of Man- 

 churia barley iu normal and clipped spikes. 



this indicates a loss, in the clipped spikes, of the photosynthetic products 

 of the awn, as well as lower transpiration, as indicated by Zoebl and 

 Mikosch, is not shown by the data. At first the difference is more 

 apparent in the weights than in the dimensions. After the twenty- 

 seventh day from the beginning of the experiment the lateral diameter of 

 the kernels from the clipped spikes begins to decrease. This is probably 

 due to the rate of loss of water in maturation, which here exceeds the 

 rate of deposit of dry matter. In the normal spikes the two changes 

 about balance each other so far as their effect on the lateral diameter 

 is concerned. The dorsoveutral diameter continues to increase until 

 full maturity in the normal spikes, while it is slightly less than main- 

 tained by the clipped spikes in the latter days. At the very last the ker- 

 nels in the clipped spikes ripen faster than those in the normal spikes. 

 This is apparent in both figure 2 and figure 3. 



