506 CONSERVATIVE ORGANS. [LECT. IX. 



tone on the upper than on the under disk: 

 but the green colour, from its being nearly uni- 

 versal, is not noticed in the description of a leaf, 

 except as regards its depth or tone ; thence, the 

 comparative terms dirty (sordidus) ; intense ( tn- 

 tensus) ; full (saturatus) ; pale (pallldus) ; and 

 diluted (dilutus). The colour is denominated olive 

 (olivaceus) when it is green with a shade of brown ; 

 and sea-green (glaucus), when it appears bluish, 

 or as if formed from a mixture of blue and green. 

 When other colours mingle with the green, the 

 leaf is termed coloured (coloratum) ; and the 

 differences of the colouring receive a determinate 

 designation : thus, when the coloured portions 

 afford the semblance of decay or disease, the leaf 

 is termed variegated (variegatum) ; spotted or 

 maculated (maculatum), when the colour is dark 

 and in spots or blotches; and zoned (zonatum), 

 when the colours are displayed in one or more 

 curved lines. The term discolor is employed to 

 denote that a leaf displays one colour on one sur- 

 face, and another on the opposite surface, as in 

 purple-leaved Spiderwort, Tradescantia discolor,. 

 two-coloured Begonia, Begonia Evansiana, &c. 



The vessels of every leaf enter it by the 

 petiole, or by the point of attachment, in fasciculi ; 

 which afterwards separate, and are spread in 

 various ways through the substance of the leaf. 

 These, when visible, form lines, which are very 



