External Conditions and Manuvinij, 321 



ria gcncrationis. The branching of the ears of Triticuni 

 tiirgiduni coniposititni (Vol. I, p. 125) and the carpello- 

 niania of Papavcr soninifcruni (Vol. I, p. 138) are to a 

 very large extent dependent on external conditions. 

 Double poppies become almost single under unfa\oraljle 

 conditions; I have observed this in Papavcr soninifcruni 

 naniini album in my own cultures. Again the doulJe 

 Saponaria officinalis plena seems to become single after 

 transplantation, but subsequently to regain its double 

 character.^ The ordinary Saponaria officinalis often 

 forms hexamerous flowers in this neighborhood. These 

 were, however, more numerous in my cultures under 

 good than under bad treatment. The studies of Pey- 

 RiTSCH on the influence of the cutting down of wood- 

 bands on peloric varieties has already been referred to 

 (§21, p. 225). On a lime tree in the vicinity of Baarn 

 pitchers are produced every year; but I always found 

 them on the open sunny side and never in parts of the 

 tree where the branches were shaded by neighboring 

 trees. 



The color is also well known to be very dependent on 

 external conditions. Achillea Mille folium rosea will only 

 form its fine red inflorescences in a sunny position; if 

 this is shaded the color is pale or absent, as I have myself 

 often observed. Inflorescences grown in the dark re- 

 main quite white, even when they would otherwise have 

 been red. The same is true of Begonia semperflorcns 

 atropiirpiirea J'^ernon, whose brown red foliage cannot, 

 so to speak, stand the smallest amount of shadow. In 

 this case I have succeeded in making some plants almost 

 quite green Iw shading them during tlicir }-<>uth. The 



* MuNTTNC, JVaarc Ocffniinficii dcr Planfni, 1671, p. 5fN'>. Al^;o In 

 my garden. 



