88 ELEMENTAL) T1SSTKS. 



The walls of the cells are thickened and often folded at the points 

 of contact between contiguous cells of the sheath. They are 

 strongly suberized, and have a clear glistening appearance. 



Illustration: ENDODEEMIS of the central cylinder in HYACINTH 

 or CORN root, grown in water. 



Make a thin trausection of an old root, and prepare as for the 

 previous study. 



OBSERVE: 1. Near the center of the root surrounding the 

 Jibro-vascular bundles a single layer of cells thickened only at the 

 points of contact, but the walls uniformly suberized, thus giving 

 them a glistening appearance, the endodermis. De Bary, p. 121 ; 

 Vine's Text Book of Bot., p. 165; Strasburger, p. 136. 



Ill Sclerenchyma Tissue. 



The cells under this tissue form vary from the short isodiametric 

 " Stone cells, " to elongated fibres, with thick walls, passing by 

 gradations into fibrous tissue on the one hand, and into cellular 

 tissue on the other, (refer to parenchyma). They will be here con- 

 sidered as distinct elements. 



Illustration: (of "Stone cells), FLESHY ROOTS of Dahlia variab- 

 ilis. 



PREPARATION FIRST: Longitudinal sections should be made 

 just 'beneath the brown epidermis. The zone containing the cells 

 will be apparent by cutting or scraping off the epidermis with a 

 knife, when the sclerenchyma tissue will be found as a hard gritty 

 layer. Mount in water. 



OBSERVE: 1. The thin walled parenchyma, making up the main 

 body of the fleshy root. 



2. Groups of Sclerenchyma cells with very thick walls; the 

 slender canals, often branched, running through the wall from the 

 central cavity. 



3. The meeting of the canals of adjacent cells. 



4. The form of the canal OJH niin/s as seen on the surface of 

 the cells. (Fig. 13.) 



PREPARATION SECOND: SCLERENCHYMA CELLS from the " IVORY 

 NUT," (Phytelephas macrocurpa} often found made into buttons, 

 umbrella handles, etc. Soire of the more common nuts may 

 be used . 



