140 MISSOURI BOTANICAL GARDEN. 



perhaps previous to, the early stages of germination. It is a 

 fact of very great interest however that this form of digestion, 

 which in Livistona takes place during the course of germina- 

 tion, occurs in the date only during the embryonic period. 

 I therefore conclude that there is secreted by the growing 

 embryo during the period from the age of about 10 weeks till 

 maturity an enzyme, probably a cytase, which causes the 

 hydrolysis of the primary walls of the developing endosperm 

 in the region of the embryo. It is to be further inferred 

 that this digestion leads to the formation of a sugar, in which 

 form it is absorbed by the embryo. 



Digestion of oil and protein — (a) During embryogeny. 

 The separation of the zone of digestion into two sub-zones, 

 a and a' in the figures, of collapsed cells within, next the 

 embryo, and uncollapsed cells further out enables us to de- 

 scribe the course of events relative to oil and protein with 

 reference to the mechanical condition of the cell walls. 



At the beginning of the period the zone (a, f. 14a) is 

 undifferentiated within itself. The cells contain only small 

 amounts of oil (f. 14) . Before the digestion of the cell walls, 

 as already described, sets in, the amount of oil increases. 

 The digestion of a column of cells in front of the embryo 

 (a, f. 15) is accompanied by the disappearance of the proto- 

 plasm and the isolation of the oil so that small droplets are 

 seen within the strand of crushed and empty cells. Assum- 

 ing for the moment that there is an actual digestion of this 

 oil, it must be slow, since there collect large droplets in the 

 space next the embryo. That the breaking down of the 

 cells at this time should proceed more rapidly than the 

 undoubtedly slow digestion of oil may be understood by the 

 fact that the volume of these cells is relatively much greater 

 than if their compression were due merely to the pressure 

 exerted by the embryo. In point of fact, this pressure is 

 exerted by the adjacent undigested cells in the direction 

 indicated by the arrow points in the figure. Now begins 

 the rapid growth of the embryo, accompanied by the com- 

 pression of the cells adjacent to its surface (f. 16), but the 

 growth of the whole endosperm in radial direction, as indi- 



