352 KiRKWOOD AND GiES : Chemical Studies 



pendent career. Neither the husk nor the shell appears to serve 

 any other than passive mechanical function, and only the constitu- 

 ents of the endosperm and milk, so far as the nut is concerned, 

 nourish the young plant before it finds in the soil the elements 

 provided there in abundance for its growth to maturity.* 



In our microscopic studies, particularly of the cotyledon, 

 pieces of the fresh part were "fixed" in a mixture of glacial 

 acetic acid (^) and 70/0 alcohol (2^). After remaining in this 

 fluid for a few hours the pieces were transferrecJ to 70^ alcohol 

 and later to 85/0 alcohol, in which they were kept. Sections were 

 cut with a razor and mounted in glycerin. Treated with iodine, 

 such sections of the cotyledon showed an abundance of starch in 

 all cells except those of the outermost layer or epidermis. This 

 outer layer stained yellow with iodine. That it contained an abund- 

 ance of oil was shown by its deep black reaction with osmic acid. 

 Large globules of oil are, however, distinctly visible in the epidermis 

 under the microscope without the aid of osmic acid. Oil may 

 also be found in the subepidermal layers, but it rapidly diminishes 

 in quantity as the distance from the outside increases and as the 

 starchy deposit accumulates. Needle-like crystals may be very 

 readily found in the epidermal cells. These resemble crystals of 

 tripalmitin, but the fact that so much oil appears in globules, and 

 that the breaking down of fats must occur to a large extent in 

 these cells, would suggest that they are palmitic acid rather than 

 the fat itself. 



The above facts make it appear that the starch is formed indi- 

 rectly at least from the oil.f See references under enzymes, 

 pages 345 and 358. 



See//, /p for drawings of parts mentioned above. 



Chemical Changes. — The following summary gives briefly 

 the effects of germination on the individual nuts examined : 



I. Not Analyzed. — A. Development had proceeded for nearly 

 six months. The plumule protruded six inches above the husk. 

 Roots had developed through the husk — two were about a quarter 

 of an inch in diameter. The stem was very thick at the " root- 



* Note references on page 357 to the functions of the husk in holding water and 

 possibly furnishing nutrient matter in its decay. 



f Ebermayer : Physiologische Chemie der Pflanzen, 347. 1882. 



