140 MISSOURI BOTANICAL GARDEN. 



HOW 



under 



be 



ternatives. The comparative absence of oil in the vicinity of 

 the embryo may be due to the immediate absorption by the 

 embryo of most of the material which would, in this region, 

 be turned into oil ; or to the movement of the oil, after it has 

 been laid down, toward the embryo. In the latter case, we 

 may assume a lipase to account for digestion, or we may as- 

 sume that the fatty material moves in the form of minute 

 globules, as Sachs believed. The occurrence of droplets of 

 oil between the embryo and the endosperm was regarded by 

 Sachs as evidence that during germination the immediate 

 entrance of this substance into the embryo is accomplished 



) of its molecule. I myself have observed the 

 occurrence of large droplets of oil in the same situation dur- 



^ & 



both 



f 



Figure 15 



otherwise. Assuming that the oil actually occurs here nor- 

 mally, it seems probable that it is due to the accumulation 

 of small droplets from the disintegration of the cells in which 

 it occurs, (zone a, f. 15). This would readily be brought 

 about if the digestion of the oil at this time did not proceed 

 as rapidly as the breaking down of the cell walls. 



The large masses of oil in the space between the haustorium 

 and the compressed endosperm during germination on the 

 other hand, I believe to be purely accidental, and is due to 

 the transposition of the oil by the knife-blade during section- 

 ing. There is, furthermore, convincing evidence that dur- 

 ing the major part of the third period of embryogeny, as 

 well as during germination, that there is an actual digestion 





sub 



of the oil, resulting in water-solul 

 therefore entirely probable that the 

 earlier periods during which oil plays a part in the nutri- 



same 



bry 



Period HI. 



The final period of development is of peculiar interest in 

 that it leads to the articulation of the two distinct physio- 



