MfSCELLANEO US. 1 1 7 



of white. Both have the leaves occasionally marked 

 in the centre with a white line or spot, which is a 

 symptom of very close relationship. Indeed, Mr. 

 Bentham formerly united the two in a single species ; 

 and even now he is doubtful whether they should be 

 regarded as more than mere varieties. When we 

 consider that all purple labiates are liable to be 

 spotted with white ; that the purple and white forms 

 are here closely allied ; that in Galeopsis tetrahit we 



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FIG. 45.--Vertical section of dead-nettle (Lamiitni albutn~) \ white, with dark lines. 



have a regular gradation from pure purple flowers to 

 almost pure yellow ones ; that in Lamium galeobdolon 

 we have a related yellow form similarly spotted ; that 

 all the Lamiums show a tendency to variegation ; and 

 that the white flower has itself an inconspicuous and 

 probably functionless variegation, where the purple 

 one has conspicuous and useful honey-guides, the 

 inference is almost irresistible that the common white 

 form, L. album, represents a retrogressive modification 



