160 FRUITS. 



(81) Black Pepper. 



The fruit of Piper nigrum, Linn. (N.O. Piperacese). 

 A transverse section of black pepper exhibits the following 

 structure : 



(1) An outer epidermis consisting of small cells with brown 

 contents and a rather thick cuticle. In surface view 

 these cells appear polygonal, and here and there a stoma may 

 be seen ; many of them contain small prismatic crystals of 

 calcium oxalate. 



(2) An outer sclerenchymatous layer abutting upon the 

 epidermis or separated from it by a single row of parenchyma- 

 tous cells. This layer is not continuous, but is interrupted at 

 intervals by thin-walled parenchymatous cells. The scler- 

 enchymatous cells vary somewhat in shape, but most of them 

 are radially elongated, and contain a brown substance ; their 

 walls are thick and pitted. 



(3) Parenchymatous tissue corresponding to the mesocarp, and 

 constituting the bulk of the pericarp. The outer layers of this 

 tissue consist of large polygonal cells, amongst which an 

 occasional still larger oil-cell may be seen ; the former contain 

 a few small starch grains, the latter globules of volatile oil. 

 The inner layers of parenchymatous cells have lignified walls 

 and are more strongly tangentially elongated or even flattened 

 so as to present a well marked line of demarcation, which is 

 accentuated by the presence of fibre-vascular bundles. Oil-cells 

 are more numerous in this inner part of the parenchymatous 

 (issue than they are in the outer. 



(4) An inner sclerenchymatous layer consisting of a single row 

 of cells thickened on their radial and inner tangential walls ; in 

 surface view these cells are seen to be isodiametric, polygonal, 

 and to have moderately thick, pitted walls ; their cavities are 

 colourless and larger than those of the outer layer of sclerenchy- 

 matous cells. This layer of cells is generally adherent to the 

 brown seed-coat. 



(5) A brown and a yellow layer of collapsed cells to which is 

 firmly attached 



(6) A colourless layer of collapsed cells ; these last three layers 

 constitute the seed-coat. 



The kernel of the seed consists almost entirely of perisperm. 

 The outer two or three rows of cells are polygonal and contain 

 aleurone grains, but the others are elongated and are packed 

 with minute grains of starch. Scattered throughout the peris- 

 perm are cells containing yellowish volatile oil. 



The diagnostic characters of powdered black pepper are : 



(a) The outer epidermis, together with the subjacent inter- 

 rupted sclerenchymatous later. 



(6) The inner sclerenchymatous layer. 



(c) The starch grains, often in compact masses. 



(d) The oil-cells, the contents of irhich are coloured red by 

 sulphuric acid. 



