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TEXTBOOK OF BOTANY 



Fig. 19. Indian pipe (left) and pinesap (right), two saprophytes common in 

 moist woods. The underground parts of the plants are penetrated throughout by- 

 fungous filaments, which enter from the humus in which the plants grow. 



of chlorophyll. We are all familiar with blanched celery in which the 

 part deprived of hght lacks chlorophyll, or with the white and yellow 

 potato sprouts that develop in a dark cellar. During the warm nights 

 of early spring bluegrass grows rapidly, and in the early morning the 

 base of the blade that grew during the night is disclosed by its lack 

 of chlorophyll. But light is not necessary for the formation of the green 

 pigments in all plants. Green seedlings of spruce, pine, and other coni- 

 fers may develop in the dark. Grapefruit and lemon seedlings, certain 

 algae, and the sporelings of mosses and ferns may produce chlorophyll 

 in darkness if they are supplied with sugar. 



Sugar is one of the substances from which the chlorophylls are made, 

 and from the formulas of chlorophyll (page 28) it is evident that com- 

 pounds of nitrogen and magnesium are also utilized. Experiments have 

 shown that manganese and iron are essential to the formation of chloro- 

 phyll, but they do not constitute a part of the chlorophyll molecule. 

 The seedlings of some green plants growing at temperatures below 



