Note 2454 — BOOK XXII. THE PROPERTIES OF PLANTS AND FRUITS.

Our “woad,” the Isatis tinctoria of Linnæus, which imparts a blue colour. The root of this Celtic woad is probably “glas,” “blue,” whence also our word “glass;” and it is not improbable that the name of glass was given to it from the blue tints which it presented. Julius Cæsar and Pomponius Mela translate this word “glastum,” by the Latin “vitrum,” “glass.”