MISCELLANEOUS. 1 1 5 



of injured parts and autumn leaves, these facts are 

 full of functional significance. 



In a single flower, the common pink Phlox, a 

 change apparently takes place in the reverse order 

 to that laid down in this treatise as the general law, 

 for it presents early in the morning a light blue tint, 

 and retrogrades to pink as the sun advances in the 

 sky. But it has been suggested (quite apart from 

 our present theory) that the blue colour is due to the 

 presence of some substance which becomes blue by 

 non-elimination of oxygen during the night ; and as 

 the oxygen is given out during the day, the blue 

 colour disappears. If this theory be well founded, 

 the apparent exception really confirms our rule. 



It has been objected by two or three authoritative 

 critics that the original petals need not necessarily 

 have been yellow, because they represent the flat- 

 tened filament, not the anthers ; and it is the pollen 

 that gives the yellow colour to most stamens. But it 

 may be answered that in the primitive yellow flowers 

 (for example, the buttercups) the filaments are usually 

 of the same golden yellow as the petals ; and in many 

 other flowers they retain more or less of a yellowish 

 tinge. In white flowers they show a strong tendency 

 to become white ; but in pink and blue ones, pink 

 or blue filaments are comparatively rare. Sometimes, 

 indeed, the filaments become brightly coloured, so as 

 to share in the attractive display ; as a rule, however, 

 they are yellow in the yellow flowers, white or greenish- 

 yellow, with more or less of a pinky tinge, in almost 

 all others. The subject is certainly one which requires 

 further investigation. 



According to Sachs, the yellow pigment of the 



