EMBRYO, SEED AND CARPEL IN THE DATE. 



147 



cated by the arrow point at the bottom of the figure, results 

 in the formation of a pit in front of the cotyledon. This is 

 obliterated only with complete maturation (f. 19). The 

 crushed layer of cells lines this pit, their crowding, which 

 does not amount to compression, still caused by the adjacent 

 tissues. The later progress of events consists in the amplifi- 

 cation of these relations till a stage represented by figure 18, 

 is reached, followed by a reduction during maturation. 



Observation during the whole of the period shows that 

 the distribution of protein and oil in these tissues may be 

 briefly summarized. 



The outermost of the uncollapsed cells (zone a) contain 

 both their oil and protoplasm in practically an unchanged 

 condition. Passing toward the embryo, the protoplasm shows 

 evidence of disintegration and obvious reduction in amount 

 till the inner layer of uncollapsed cells is reached, where only 

 the oil remains usually as a single drop in each cell. 

 Within the crushed layer, these oil drops are quickly reduced 

 in size (f. 18a and 20). 



(b) During germination.— 



—The zones 29 of digestion sur- 

 rounding the growing haustorium are as follows, beginning 

 at the plane of contact with the embryo (f. 24; text figure 

 B). The thickness of the zones depends upon the position 

 relative to the haustorium, being thickest opposite the rap- 

 idly advancing edges : 



a. Crushed cells derived from embryonic period, reacting blue with 



iodine. This zone is discontinuous and is derived from the 

 resting condition. 



b. A zone of compressed cells, of primary membranes only, about 



15 microns thick. The oil is in minute droplets. (Sachs' 

 layer 1). 



c. A zone in which the oil is in a large single drop in each cell; the 



protoplasm has disappeared. The reserve cellulose is less in 

 amount proceeding toward the embryo and the cells are 

 more compressed (text figure b). (Inner part of Sachs' 



\ 



middle layer.) 





19 The reader will not infer that these zones are sharply delimited, 

 any more so than the others which I have described. Nevertheless, 

 they represent an objective reality. - 



