What are sclereids? Write briefly their different types.

Explanation

Sclereids. The sclereids are small unbranched or branched sclerenchyma cells hav.ing branched or unbranched lumen. The lumen is generally broad. These provide mechanical support. They are present in the grit of apple, tea leaves etc. TI1e sclereids are of following types.
(i) Stone cells or brachysclereids. These are polygonal having branched narrow lumen. These are present in grit of apple and pear.

(ii) Macrosclereids. They are elongated sci ere ids having unbranched broad lumen. They are present in epidermis of seed coats ofleguminous plants.
(iii) Osteosclereids. These are bone like sclereids having knobs at either end. These have unbranched lumen. These are present in sub-epidermis of seed coats of leguminous plants.
(iv)Astro sclereids. These are branched and have branched lumen. They are present in the leaves of tea, lotus etc.
( v) Filifonn. These are branched sclereids which are narrow with narrow branched lumen. These are present in leaf of Olea.