Botanic characteristics
Unground Plantago psyllium Seed
Ovate to ovate-elongate,concavo-convex;mostly from 1.3to 2.7mm in length,rarely up to 3mm,and from 600µm to 1.1mm in width.It is light brown to moderate brown,darker along the margin,and very glossy;the convex dorsal surface exhibiting a lighter colored longitudinal area extending nearly the length of the seed and representing the embryo lying beneath the seed coat,and showing a sometimes indistinct transverse groove nearer the broader end.The concave ventral surface has a deep cavity,in the center of the base of which is an oval,yellowish white hilum.
Unground Plantago indica Seed
Ovate-oblong to elliptical,concavo-convex;from 1.6to 3mm in length and from 1to 1.5mm in width.Externally it is dark reddish brown to moderate yellowish brown,occasionally somewhat glossy,often dull,rough,and reticulate;the convex dorsal surface having a longitudinal lighter colored area extending lengthwise along the center and beneath the seed coat,and a median transverse groove,dent,or fissure.The ventral surface has a deep concavity,the edges somewhat flattened and frequently forming a sharp indented angle with the base of the cavity,the latter showing a light colored oval hilum.
Unground Plantago ovata Seed
Broadly elliptical to ovate,boat-shaped,from 2to 3.5mm in length and from 1to 1.5mm in width.It is pale brown to moderate brown with a dull surface,the convex surface having a small,elongated,glossy brown spot.The concave surface has a deep cavity,in the center of the base of which occurs a hilum covered with a thin membrane.
Odorand taste
All varieties of Plantago Seed are nearly odorless.
Histology
Plantago Seed is reniform in median transverse sections.Its seed coat has a colorless epidermis of mucilaginous cells whose radial and outer walls break down to form layers of mucilage when brought into contact with water,and a reddish brown to yellow pigment layer in the seeds of Plantago indicaand Plantago psyllium,a broad endosperm with thick-walled outer palisade cells,and irregular inner endosperm cells;and a straight embryo extending lengthwise through the center.The endosperm and embryo cells contain fixed oil and aleurone grains,the latter being rounded,oval,pyriform,or irregularly shaped,from 2to 8µm in diameter.