2l6 PHARMACEUTICAL BOTANY 



4. The Endosperm or nourishing tissue, consisting of: (a) The 

 Aleurone Layer, for the most part a single row of cells, containing 

 aleurone grains. Some of the cells may be seen to be divided by 

 tangential partitions, (b) Starch Parenchyma, consisting of two 

 regions: an outer horny zone composed of cells containing for the 

 most part polygonal starch grains and oil droplets; and an inner 

 mealy zone of cells with mostly rounded starch grains. 



5. The Embryo, consisting of a single shield-shaped cotyledon 

 adjoining the endosperm, the plumule or rudimentary bud at the 

 end of the caulicle or rudimentary stem and the radicle or rudimen- 

 tary root, with its tip covered by a root cap. Continuous with the 

 root cap is a root sheath or coleorhiza. The cotyledon or seed leaf 

 consists of two parts : the scutellum which lies next to the endosperm, 

 and is an organ of absorption; and the sheafing portion which sur- 

 rounds and protects the rest of the embryo. 



The embryo contains oil and proteids, but no starch. 



If a similar longitudinal section of a soaked grain be mounted in 

 dilute iodine solution, the contents of the aleurone cells will be col- 

 ored yellow indicating their proteid nature, while the starch grains 

 will take on a blue to violet coloration. The endosperm will be 

 observed taking up most of the room within the seed coat. The con- 

 tents of its cells are not baled out to the embryo until after germina- 

 tion begins. Indian Corn is therefore an albuminous seed. 



A MONOCOTYL SEEDLING 



Germination. When any viable seed is planted in suitable soil, 

 and furnished with oxygen and water and a certain degree of heat, 

 germination takes place. In the presence of moisture, etc., the seed 

 swells, the ferments present within the cells of the endosper n then 

 change the insoluble proteid, starch, and oil to soluble materials, 

 which, in the case of Indian Corn, are absorbed in solution by the 

 scutellum which bales this nourishment out to other parts of the 

 growing embryo, there to be used in part in constructing new tissues, 

 and in part to be consumed fry oxidation or respiration. The process 

 of respiration or breathing takes place when the plant takes in oxy- 

 gen and gives off carbon dioxide. The oxygen oxidizes the tissues 



