No. 439 ] NORTHERN GAM OPETALOUS FLOWERS. 463 



side. From indigo may readily he obtained aniline remarkable 



In darkness flowers differ greatly in the extent to which they 



ing and Prunella o T audijlo\I xx^W^\ of developing dark violet 

 color remains ~a pure white ; while Titjipa gesncriana forms its 

 red color and Crocus vermis its blue violet as perfectly in dark- 

 ness as in light. The explanation given by Sachs, where bulbous 

 plants produce normal flowers in darkness, is that the flower 

 forming substance was already collected in the bulb, and had 

 been stored up in a preceding period of vegetation in bright 

 sunlight. Leaves, flowers and fruits often display red coloration 

 only on the side exposed to direct sunlight. Kerner found that 

 the anthocyan in plants grown in an Alpine garden at an eleva- 

 tion of 2195 metres above the level of the sea was brighter 

 colored and more abundant than in the botanical garden at 



