RELAPSE AND RETROGRESSION. 79 



blue or purple. So, again, another English labiate, 

 Galeopsis tetrahit, the hemp-nettle, has a pale purple or 

 white corolla, sometimes with a tinge of yellow in the 

 throat : and in the var. versicolor, the yellow spreads 

 over all the flower, except a purple patch on the 

 lower lip. In G. ochroleuca, the whole corolla has 

 become pure yellow. In this way, one can under- 

 stand the occurrence of such a flower as Lamium 

 galeobdolon, especially since an allied species, L. album, 

 is white, and all the genus is extremely variable in 

 colour. Indeed, it is to be noted that the yellow 

 labiates do not commonly occur among the less 

 developed thymes, mints, and marjorams, but among 

 the extremely specialised Stachydece, which have very 

 modified flowers, and usually variegated or spotted 

 lips. They seem to be essentially reversionary forms 

 from purple or blue species, spotted with yellow. 

 Nay, the lower lip of L. galeobdolon itself still shows 

 marks of dark orange variegation, exactly answering 

 to that of several purple Lamiums : and the base of 

 the corolla tube is still pink or purplish. 



Another hint of Retrogression is given us by flowers 

 like our English balsams, Impatiens noli-me-tangere 

 and /. fulva, in the fact that their yellow is generally 

 dappled with numerous spots of deeper colour. The 

 balsams are highly modified irregular Geraniacece, 

 sepals and petals being both coloured : and at first 

 sight it seems curious that our species should be 

 yellow, while the simpler Geraniums and Erodiums 

 are pink or red. But the genus as a whole contains 

 many red and variegated species, and alters in colour 

 with much plasticity under the hands of gardeners. 

 /. noli-me-tangere is pale yellow spotted with red : 



