MISCELLANEOUS NUTS. 31 



end and rather pointed at the other. To the radicle, located at the 

 more acute end of the grain, are attached the two large green cotyle- 

 dons. These are so placed that one edge of each occupies an angle 

 of the nut, which is, therefore, quite acute. The other edges of the 

 cotyledons are flattened, and have a conspicuous depression near the 

 distal end. The seed coat is thickest over the acute edges of the 

 cotyledons and an adjacent semicircular area on each side of the 

 nut. The endosperm is thickest near the border of this area and that 

 surrounding the radicle. The thicker portions of the seed coat con- 

 tain a dark red coloring matter, while the thinner portions are 

 colorless, and show the green color of the cotyledons beneath. 



Pistachio nuts are offered for sale in the larger cities, and are used 

 to some extent in confections, etc. They have a peculiar, pleasant, 

 and somewhat resinous flavor. It is said that other nuts are oc- 

 casionally colored green in imitation of pistachio nuts. 



Histology. The epidermis of the seed coat consists of cells of 

 variable shape, in some parts of the nut quite regular with few inter- 

 cellular spaces, in others very irregular with many large or small 

 spaces between the cells. They vary in extreme diameter from 15 

 to 160 (& (PL IV, fig. 1). In the transverse section (PL IV, fig. 2) 

 an outer and an inner layer of periderm can be distinguished, 

 although they are usually not sharply differentiated. The outer 

 layer consists of a spongy tissue, the innermost cells of which are in 

 some regions provided with thick walls, resulting in grotesquely- 

 shaped sclerenchyma cells (PL IV, fig. 5). The inner layer, con- 

 sisting of smaller and more regularly-shaped cells^ contains the 

 vascular bundles in the outer part. 



The endodermis of the seed coat consists of polygonal cells, averag- 

 ing about 8 [A in diameter, which have thick, beaded walls of char- 

 acteristic appearance (PL IV, fig. 3). This layer is only about 5 \L 

 thick; when viewed in cross section a few of the cells are seen to be 

 divided by horizontal walls. It is not continuous, since it fades 

 away into the parenchyma tissue of the thicker portion of the seed 

 coat, where the latter becomes continuous with the perisperm. 



The perisperm is the most restricted of all the tissues surrounding 

 the embryo, as it underlies only the thickest area of the seed coat, 

 is continuous with it, and spreads out under the endodermis as a 

 thin sheet of collapsed-looking cells, which gradually thins out and 

 disappears. In restricted areas it is somewhat thickened and con- 

 tains needle-shaped bodies resembling crystals, but without polari- 

 scopic activity. 



The endosperm likewise is not continuous and varies considerably 

 in thickness. It constitutes a layer two or three cells in thickness 

 under the thicker portions of the seed coat, becomes thicker toward 

 the borders of this region, and then gradually disappears so that 



