Manchester Memoirs, Vol. liv. (1910), No. 18. 



XVIII. Note on the Variability in the Colour of the 

 Flowers of a Tropaeolum Hybrid. 



By F. E. Weiss, D.Sc, FX.S. 



Read [annary nth, icpio. Received for fuf>l!caiioii July 22nd, igio. 



In the summer of 1908 my attention was attracted 

 to a plant among the Nasturtiums in my garden, which 

 bore flowers of different colours, some quite light yellow 

 with dark honey guide, while one was of red colour. The 

 plant was still young, so I potted it up and watched its 

 later developments. During the summer it produced a 

 large number cf flowers, apparently with complete irregu- 

 larity, as could be seen from a diagrammatic plan of the 

 different branches, on which the different coloured flowers 

 were indicated. It became apparent also that the flowers 

 were not all of two distinct types, but shaded off from 

 one extreme to the other. Thus, besides the completely 

 yellow flowers, some appeared with slight red blotches at 

 the edge of the petals, and these increasing in size and 

 extending to the base of the petals were found in every 

 stage until the whole petal was scarlet, the last part to 

 become scarlet being the little fringe at the base of 

 the expanded portion of the petal. In the autumn 

 brownish patches became frequent on the petals leading 

 to a darker coloured flower. But though this was the 

 case both in the autumn, and as long as the plant 

 remained alive during the winter, some yellow flowers 

 were always to be found among the parti-coloured ones. 

 The yellow colour of the petals is due to yellow chromo- 

 plasts, while the supervening red or brown colour is due 

 to coloured cell sap. 



August jisf, igio. 



