92 



R. A. BRINK 



15.6, a value equal to the mean. The range is even greater in the class of 

 seeds having 128-cell endosperms, and the standard deviation rises to 51 

 cells. 



The extreme variability in embryo size for given stages of endosperm de- 

 velopment in T. officinale is a fact of cardinal importance in the present 

 analysis. Inspection of Table 5.2 reveals certain details which emphasize 

 the significance of the summary data on dispersion. Note, for instance, that 



TABLE 5.2 

 DISTRIBUTION OF EMBRYOS BY CELL NUMBER RELA- 

 TIVE TO ENDOSPERM DIVISION CYCLE 

 (AFTER COOPER AND BRINK, 1949) 



among the seeds still in the endosperm mother cell stage (0 cycle) one con- 

 tains an embryo in the 128-cell class and seven have embryos in the 64-cell 

 class. Similar, although less extreme, cases occur in the 1 -cycle and 2-cycle 

 endosperm distributions. Study of the histological preparations shows that 

 the seeds in which the embryos are found are growing vigorously and appear 

 capable of completing development. This can mean only that either very 

 small endosperms in T. officinale are extraordinarily efhcient structures, or 

 embryo growth in this species is not dependent on an endosperm. 



At the opposite corner of the table, on the diagonal, two seeds are entered 

 in the 7-cycle endosperm array in which the embryos are still in the one-cell 

 stage. These seeds also appeared to be healthy and capable of continued 



