size, compared to other parenchyma cells that only increase by two or three times. Fruit sclereids Sclereids in fruits vary in form and use. In pears, sclereids from concentric clusters that grow about earlier formed sclereids. These pear sclereids, as well as sclereids within quince fruit, often form bordered pits when the cell wall increases in thickness during sclerification. In apples, layers of elongated sclereids form the endocarp that encloses the seeds. Seed sclereids The hardening of seed coats during ripening often occurs through sclerification, when the secondary cell walls are thickened in the epidermis and below the epidermis. Leguminous seeds are examples of such sclerification. Larger sclereids form columns in the epidermis of pea, bean, and soybean seeds, and bone-shaped osteosclereids occur beneath the epidermis. In the seedcoats of coconuts, sclereids possess numerous bordered pits. These larger macrosclereids found in seedcoats are of protodermal origin. References Further reading Chrispeels MJ, Sadava DE. (2002). Plants, Genes and Crop Biotechnology. Jones and Bartlett Inc. . Moore, Randy; Clark, W. Dennis; and Vodopich, Darrell S. (1998). Botany (3rd ed.). McGraw-Hill. . Plant anatomy Plant cells Tissues (biology)