TISSUES AND SIMPLE ORGANS. 



151 



(5) The Storing of Starch and Other Food-substances, Especially 

 the Albuminous Substances. 



Entire organs and complexes of organs, even entire plants, 

 have at times the character of reservoirs for reserve materials. 

 Parenchyma, medullary rays, cortical tissue, and especially the 

 woody tissue of trees during winter, may serve as storage-tissue. 



Sometimes nitrogenous (especially albuminous) and non-nitro- 

 genous (carbohydrates, fatty oils) substances occur in one and the 

 same tissue. Protoplasm and starch 

 occur in the potato, protoplasm and 

 dissolved sugar in the beet, protein- 

 granules (albumen) and starch in the 

 cotyledons of beans, peas, and lentils. 

 In other cases the reserve carbo- 

 hydrates occur in the form of cellu- 

 lose : thick-walled cells with numer- 



FIG. 91. Section of the peripheral 



portion of a grain of wheat. 

 5, Seed-coat; kl, gluten-bearing layer; z, 



starch-bearing endosperm-cells. (X 300.) 



(After Haberlaudt.) 



FIG. 92. 



A, Iris-seed in tangential longitudinal sec- 

 tion. B. Cross-section of the same in the 

 direction ab. C, Seed of Anethum Sova 

 in cross-section. The arrangement of 

 the endosperm-cells is indicated by the 

 lines. (Schematic.) (After Haberlandt.) 



ous pores form the storage-tissue of Fritillaria imperialis, of the 

 date-palm, of Phytelaphas macrocarpa (" vegetable ivory"), and 

 of Coffea arabica. In most of our grasses albumen and carbo- 

 hydrates occur separately in different tissues ; the cereals contain a 

 peripheral layer bearing protein-grains (gluten-bearing layer), while 

 the mass of the storage-tissue contains the starch and a small amount 

 of protein (Fig. 91). 



The storage-cells are sometimes strikingly arranged in straight 

 rows or in curves. Such arrangement may be dependent upon 

 mechanical or physiological requirements. The mechanical prin- 



