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MISSOURI BOTANICAL GARDEN. 



the region of digestion had by this time spread along the 

 flanks of the cotyledon. In two seedlings in which the first 

 foliage leaf was 3.5 cm. long, in which therefore the haus- 

 torium was quite large and nearly fully developed, I found 

 the oil very unevenly distributed. In most of the epithelium 

 cells there was none. A comparatively few cells in isolated 

 groups showed a rich oil content. In no case was there any 

 oil in the parenchyma below. In a similar seedling after 

 a week's exposure to ethyl nitrite, there was a very large 

 oil content, the epithelial cells being quite replete, 31 so that 

 one could hardly observe the remaining contents. Scarcely 

 a cell varied from this condition. Similar results were ob- 

 tained in a younger stage when the first foliage leaf was 

 just emerging. 



1 The conclusion is therefore drawn that the disappearance 

 of oil during the development of the embryo and during 

 germination is due to the same cause, namely, digestion. 

 This digestion results in the formation of water-soluble sub- 

 stances, and not of an emulsion. The reappearance of oil 

 in the embryo is due to its reformation from these sub- 

 stances in consequence of the failure of the embryo to con- 

 sume them as rapidly as formed. 



The particular behavior of the protein I have not espe- 

 cially considered, beyond to note the time of its disappear- 

 ance from the cell relative to that of the oil. Sachs believed 

 that "albumen" enters the embryo "as such." It is appar- 

 ent that this material must undergo proteolysis if we accept 

 evidence of the same character as that advanced with regard 

 to oil and cellulose. 



The Tension Zone.— The limits of the various zones are 



■ 



not sharp, so that, in making diagrammatic representations 

 there is necessary some compromise as a sacrifice to con- 

 fusing detail. In the first stage considered (f. 14a) the 

 tension zone is little more than a vague layer of cells (b) 

 somewhat crowded between the digestion zone a and the thin 



31 A large increase in the starch content of the parenchyma beneath 

 the epithelium was also noted. 



