EMBRYO, SEED AND CAEPEL IN THE DATE. ' 145 



crushed walls next the embryo, as com 



same 



elusion. It may finally be noted that the earliest mechanical 

 disruption of cells is not due to the pressure of the embryo 

 upon the contiguous endosperm cells, but of the cells of 

 zone a upon those of a (f. 15). It takes place previous to 

 the secondary thickening of the endosperm walls by the 

 deposition of reserve cellulose. As the embryo grows, the 

 amount of tissue thus affected increases markedly (f. 16, 17) 



time of maximum activity is reached 



about 



by figure 18. The reaction obtained 



time indicates that zone a (f. 18) may reach quite near 



to the outer limit of zone b. My preparations show further 

 that the blue reaction is not always confined to the cell wall, 

 but may frequently fill the lumen, indicating the presence 

 of a soluble or colloidal substance here. 28 On approach to 

 maturity, the relative thickness of the layer of cells affected 

 becomes reduced, and at the time of ripening, occupies the 

 zone a shown in figure 19. I have verified this by control 

 with commercial dates, which give the same reaction. 



During the early stages of germination I have found only 

 a partial reaction and this is confined to the endosperm in 

 contact with the older part of the growing haustorium ( f . 24, 

 25). In a stage corresponding to figure 25, the blue reac- 

 tion appeared along the flanks and around the end of the 

 cotyledon, but in the latter position it was very thin and 

 discontinuous. In a somewhat older condition, as in figure 

 24, the reaction was to be seen only along the sides of the 

 haustorium, corresponding to the extent of the sides of the 

 cotyledon seen in figure 25. It seems probable therefore 

 that the change of the primary membranes into an amyloid 

 is chiefly an embryonic phenomenon, and ceases during or 



28 I have found some evidence that a small amount of starch in the 

 form of minute granules occurs. These are scattered between the 

 crushed cell walls. The amount seen however is very small, and I 

 have not always been certain of its presence. This uncertainty may 

 be due to its disappearance ana reappearance. 



