382 



Vegetable Physiology. 



A cross section of one of 'the fibro- vascular bundles of the stem of the white lily : a, cellular' tissue 

 (next the centre of the stem) ; b, spiral and other vessels and ducts ; c, cambial or sap cells ; 

 d, liber cells ; e, cellular tissue next the rind. 



Fig. 6. 



A perpendicular section of the same, giving a side view of the cells and vessels. The letters with 

 the same signification as in the upper figure. Both magnified 100 diameters. 



of rhubarb are almost wholly composed of cells containing these 

 spiral and annular layers of thickening', and afford a very con- 

 venient opportunity of studying their characters ; they may also 



