ALLIED AND MISCELLANEOUS PRODUCTS 195 



are dependent upon sugars, whatever makes for abundant sugar 

 in the leaves makes for bright autumnal coloration. When the 

 change from summer to winter is abrupt with early frosts, there 

 will be more sugar in the leaves, since the leaves have been con- 

 stantly at work with no diminution in their activity. Bright days 

 produce sugars, and are also more likely to be followed by frosts 

 than cloudy ones. Thus the conditions in regions like Eastern 

 Canada and New England are ideal for brilliant autumn foliage. 

 The frost comes early, the summer ends abruptly, and the autumn 

 is bright, resulting in the gorgeous effects produced in these places. 



Classification of pigments according to color and cause: 

 Brown — tannin, fucoxanthin, phycophrein (?) 

 Blue — alkaline anthocyans. 



Green — chlorophyll, mixtures of yellow and blue. 

 Red — phycoerythrin, lycopersicin, acid anthocyans. 

 Yellow and orange — carotinoids, anthoxanthins, flavones. 

 Violet — neutral anthocyans. 



QUESTIONS 



1 . What are terpenes? phenols? 



2. Is phycoerythrin more nearly related to anthocyan or to lycopersicin? 



3. What colors have flowers pollinated by night-flying insects? 



4. Do flowers appear the same color to bees as to man? 



5. Plants grown in the absence of nitrates are generally rich in anthocyan. 



Why? 



6. Give the derivation of the following words: phycoerythrin, lycopersicin, 

 phycophsein, anthoxanthin. 



7. Name two ways in which tannins may protect against fungi. 



8. What is an ampholyte? Give examples from this chapter. 



9. Why is wine made from blue grapes generally red? 



REFERENCES 



Arthur, J. M. — Red pigment production in apples by means of artificial 



light sources. Contr. Boyce Thompson Inst., 4:1, 1932. 

 Denny, F— Hastening the coloration of lemons. J. Ag. Res., 27:757, 1924. 

 Dobbin, L.— The presence of formic acid in the stinging hairs of the nettle. 



Proc. Roy. Soc. Edinburgh, 39:137, 1919. 

 Forster, M. — The laboratory of the living organism. Nature, 108:243, 1921. 

 Heilbron, I. — Plant pigments. J. Soc. Chem. Ind., 43:89, 1924. 

 Keener, A. — The factors concerned in the reddening of the leaves of Diervilla 



lonicera. Am. J. Bot., 11:61, 1924. 

 Kraemer, H.— Plant colors. Am. J. Pharm., 93:414, 1921. 

 Latham, R. — The color of primrose flowers. Nature, 107:301, 1921. 

 Lloyd, F. E.— The occurrence and functions of tannin in the living cell. Trans. 



Roy. Soc. Canada, 16:1, 1922. 



