12 STUDY OF NUTS MICKOSCOPIC IDENTIFICATION. 



of bitter almonds. Although the oil obtained from the seeds is prac- 

 tically the same in composition and properties as that distilled from 

 bitter almonds, 1 and its use is allowed by the United States Pharma- 

 copoeia, 2 the wisdom of labeling such products strictly according to 

 their origin can not be urged too strongly upon manufacturers and 

 dealers. The apricot, peach, and prune seeds resemble those of the 

 almond in structure, but differ from them in certain characteristic 

 details, so that adulteration or substitution may readily be detected. 



APRICOT KERNEL. 



(Prunus armeniaca L.) 



Apricot kernels (fig. 1, C), usually thinner than the almond but 

 thicker than the peach kernel, are nearly circular or slightly oval in 

 outline, with a small but distinct point marking the location of the 

 radicle. They have nearly the odor and flavor of bitter almonds, but 

 the bitterness is less intense. Apricot pits are better adapted than 

 those of the peach as a substitute for bitter almonds, since the shells 

 are thinner and the kernels larger and thicker, amounting to from 

 20 to 25 per cent of the weight of the entire pit. 3 



Histology. The epidermal cells of the integument are from 50 to 

 100 [JL in diameter, averaging about 75 pi or a little less. They have 

 thin, slightly beaded walls. The epidermal stone cells are scattered 

 over the surface with remarkable evenness, usually singly but some- 

 times two or three in contact (PL II, fig. 3.) This evenness of dis- 

 tribution is not affected by the vascular bundles, as is so noticeable in 

 the case of the peach, although the stone cells average somewhat 

 smaller over the vascular region than over the surface generally. 

 They are polygonal, or roundish, in outline, slightly hollowed where 

 adjacent to intercellular spaces. The inner and lateral walls are 

 marked with numerous round pores, a few of which are found also 

 in the much thickened outer wall. The latter never appear to pro- 

 trude sufficiently to suggest trichomes; they vary in diameter from 

 25 to 125 pi, averaging usually about 75 n, and their height is seldom 

 greater than their horizontal diameter. Hannig 4 has called attention 

 to a characteristic appearance of the vascular bundles in the seed coat 

 of the apricot. These bundles usually present the appearance of two 

 parallel lines of vascular tissue with a clear space between, and give 

 off many branches, usually at a large angle with the main bundles.. 

 The remaining tissues of the seed coat contain no characteristic 

 elements and the parenchyma layer is without rosette crystals. The 



1 Rabak. Peach, Apricot, and Prune Kernels as By-products of the Fruit Industry in 

 the United States. U. S. Dept. Agr., Bureau of Plant Industry Bui. 133, p. 25. 

 2U. S. Pharmacopoeia, 8th rev., 1907, p. 306. 

 3 Rabak. Loc. cit., p. 28. 

 *Zts. Nahr. Genussm., 1911, 21: 585. 



