THE PRINCIPAL TISSUES. 



73 



(d) The hard tissues of nuts and of stone fruits furnish excellent ex. 

 araples of short and very thick- walled sclerenchy ma-cells. In the 

 hickory nut (Carya alba) the cells (Figs. 58 and 59) are not more than 



FIG. 58. 



FIG. 59. 



Fig. 58. Sclerenchyma-cells of the shell (endocarp) of the hickory-nut ( Carya 

 alba), taken parallel to the surface of the nut. X 400. 



Fig. 59. Sclerenchyma-cells of the shell (endocarp) of the hickory-nut (Carya 

 alba), taken at right-angles to the surface of the nut. X 400. 



two or three times as long as broad, and the thickening is so great as 



.almost entirely to obliterate their cavities ; the thickened walls are 



r a 



FIG. 60. 



FIG. 61. 



Fjg. 60. Sclerenchyma-cells of the seed-coat of Echlnocystis lobata, from a section 

 at right angles to the surface of the seed ; a, a cell cut directly through its centre, 

 showing the whole of the cavity the three dark spots are probably oil ; &, a cell 

 cat through at one side of the middle ; c, a cell whose cavity was not cut into in 

 making the section. X 250. From a drawing by J. C. Arthur. 



Fig. 61. Sclerenchyma-cells of the seed-coat of Echinocustis lobata, from a section 

 parallel to the surface of the seed. X 250. From a drawing by J. C. Arthur. 



pierced by many deep pits. The cells are arranged with their longer 

 axes perpendicular to the surface of the nut, and are very closely 

 packed together. 



