ETIOLATION. 295 



the epidermis) of colored cell-sap. This is sometimes in such 

 large amount as to mask completely the green granules which 

 are contained in the same cells. 



786. In the Florideae (rose-red marine algae) the chlorophyll 

 is masked by the presence of a reddish coloring-matter which is 

 easily extracted by pure water. This reddish pigment is called 

 phycoerythrine. In solution it is carmine-red by transmitted, 

 and orange by reflected light. Analogous pigments extracted 

 by water from algae of colors other than red have received 

 the following names, phycophaeine (brownish), phycocyanine 

 (bluish), phycoxanthine (yellowish-brown) . 



When these coloring-matters have been extracted by cold 

 water, the chlorophyll is left unchanged in the plant, and it 

 then imparts to the thallus its characteristic green color. Owing 

 to the nearly complete insolubility of these reddish pigments in 

 alcohol, and the complete solubilitj' of the chlorophyll pigment 

 in that liquid, a green color is given at once to alcohol when an 

 alga is immersed therein. 



787. Colored bodies, not readily, if indeed at all, distinguish- 

 able from ordinary crystalloids (see 177), are found in many 

 algae. In some cases these colored granules of crystalline form 

 occur normally in the living plant ; in others they arise from 

 changes produced by the action of reagents upon the matters of 

 the cells. The name rhodospermin, given by Cramer to the 

 granules having the latter origin, has been adopted by Klein in 

 an extended memoir. 



788. Etiolation. Green plants placed in darkness soon turn 

 pale and become blanched or etiolated. The chlorophyll gran- 

 ules change their color, and finally appear to become merged, 

 with more or less change of form, in the protoplasmic mass, 

 from which they are then no longer easily distinguishable. Etio- 

 lated pla.fts when exposed to light recover their color only when 

 the temperature is above a certain point. The action of light in 

 restoring color is, moreover, local, being confined to the part of 

 the plant which is exposed to its influence. It may be here 

 noted that some plants are not etiolated until after long expos- 

 ure to darkness ; thus the older parts of Cactus speciosus, kept 

 in the dark, remained green for three months, but the new shoots 

 were etiolated. Selaginella remained green from four to five 

 months. 1 



1 Sachs : Handbuch der Experimental -physiologic, 1865; also Botanische 

 Zeitung, 1864, and Flora, 1863. 



