Aug. 2, 1920 Daily Development of Kernels of Hannchen Barley 407 



The significance of the data in Table II is, perhaps, more easily seen 

 in figure i. The most surprising feature shown by this figure is the 

 remarkably rapid growth in length following fertilization. In the two 

 days from the second to the fourth after fertilization, half the growth in 

 length occurs. The insufficiency of 3-day intervals in sampling at this 

 stage is obvious. Distinct growth is shown in 12-hour periods, and it 

 is probable that consistent increase would be revealed in 6-hour periods. 

 The kernel reached its maximum length by the end of 7 days in each 

 year. After the peak of length is reached, there is a gradual decrease 

 to maturity. This is discussed later in connection with figure 4. 



The lateral diameter exhibits its most rapid increase as soon as the 

 rate of the growth in length diminishes. This increase continues until 

 about the fifteenth day, after which the lateral diameter remains more 

 or less stationary. The dorsoventral diameter, on the other hand, 

 continues to increase almost until maturity. The increase is somewhat 

 less than in the lateral diameter, there being a greater divergence in 

 the growth curves at the end of the growing period than at the beginning. 

 The effect of the better irrigation in 191 6 is apparent throughout the 

 period of growth. There is a possibility that the 191 6 samples are a few 

 hours farther advanced throughout the series because of differences in 

 temperature or other factors at flowering time. While growth itself is 

 not so easily affected, fertilization is often hastened or delayed many 

 hours by conditions in the environment. 



During the early growth of the kernel the ovary tip undergoes a sym- 

 pathetic development. When the kernel is first developing, the growth 

 is largely in the pericarp. Some of the tissues surrounding the embryo 

 sac and the ovary walls of the same region develop rapidly and are to be 

 found in the ripened caryopsis. For some reason, the tissues above the 

 embryo sac are temporarily stimulated, forming a body at the end of the 

 kernel, which is referred to here as the ovary tip. This growth, which 

 may be seen in Plates 83 and 84, is of importance because it introduces an 

 error in the measurement of length. After the growth of the first few days, 

 this organ remains stationary in size for a while and finally is largely 

 resorbed. In figure i it will be seen that it was possible to measure the 

 kernel proper without this tip by the fifteenth day after flowering. The 

 records of lengths until that time included the ovary tip. The lateral 

 and dorsoventral diameters of the ovary tip are shown in figure 4. It is 

 probable that the length of the kernel proper increased somewhat after it 

 had apparently reached its maximum by invading the tissues of the 

 ovary tip. This tissue is probably partially responsible for the differ- 

 ence of measurements in the first 15 days of the two years. A second 

 factor in the error lies in the softness of the structure at the base of the 

 kernel. In the early stages of growth it is exceedingly difficult to place 

 the caliper bar at exactly the right point, and in 1917 the kernels may 

 have been measured more closely than in 191 6. The difference of the 



