COLOR OF PLANTS 1 5 



Color 



18. Plants are usually green. This is so commonly true 

 that perhaps the most general idea associated with the term 

 plant is that of the green color. There are, however, many 

 plants that are not green, as, for example, the ''dodder" and 

 ''Indian pipe." But these plants are also exceptional in other 

 ways. The red and brown sea weeds and plants like the 

 coleus are apparently exceptions, but in these cases the green 

 is really present, though masked by other coloring matters. 

 Besides, there is a large group of organisms like toadstools 

 and molds, collectively called fungi, which are not green. 

 These organisms are grouped by the biologist with the plants, 

 but they are evidently very different from what is commonly 

 meant by "plants," and for the present we may leave them 

 out of consideration. So we may say that, with some excep- 

 tions, those organisms which are commonly called plants, are 

 green. Such uniformity of color is not found among animals 

 and, therefore, it is worth while to ask, why are plants so 

 uniformly green? 



19. Most plants which are normally green lose their color 

 when grown in the dark. Thus grass growing beneath a stone 

 is yellow; celery is blanched by covering it, and the shoots of 

 potatoes sprouting in a dark bin have no trace of green. 



20. Exposure to sunlight soon produces the familiar green 

 in the leaves and certain parts of the stem of such etiolated 

 plants. Frequently those parts of a plant which are not nor- 

 mally green become so on exposure to sunlight. This occurs 

 when, for example, the tubers of an Irish potato, normally 

 underground, are exposed by removal of the soil. The same 

 is true of the roots of many plants. 



21. Furthermore, it will be found that no green plants will 

 continue to grow in places where they can get no light; while 

 on the other hand fungous growths like toadstools flourish in 



