98 PHYSIOLOGICAL CONDITIONS AND FACTORS [CH. 



Bellis perennis. In 15 % sugar solution green leaves developed 

 a weak red coloration only in the light, and it was confined to the 

 epidermal cells. 



Thus we see that Katie's results differ from those of Overtoil in two 

 points. First, anthocyanin may develop in sugar cultures in the dark, 

 and secondly, it is not necessarily confined to the epidermis. 



The question of the results of sugar-feeding has been taken up more 

 recently (1912) by Gertz (386). The following account is taken entirely 

 from his paper. He deals with a point in Overtoil's results we have just 

 mentioned, i.e. the statement that by sugar-feeding anthocyanin can be 

 induced to form in the mesophyll, but not in the epidermal cells. Thus it 

 would appear possible that the chloroplastids might have some influence 

 on the formation of pigment, and the failure of petals to produce antho- 

 cyanin in sugar culture might be considered a corroboration of this 

 view. In Vallisneria spiralis and Elodea, Overtoil found epidermal 

 anthocyanin on sugar culture, but this is no proof, since the epidermis 

 in those plants contains chlorophyll. General evidence is, moreover, 

 against the view of the connection with chloroplasts, as the epidermis 

 often contains anthocyanin, and this pigment is also developed in 

 chlorophyll-free saprophytes and parasites and in perianth leaves. 



In order to investigate this point, Gertz made some sugar culture 

 experiments with parts of albino leaves which were free from chloro- 

 plastids. For this purpose he used first the leaves of Oplismenus 

 imbecillis (Graminaceae), and found that anthocyanin may be induced 

 to form in the complete absence of chlorophyll. Therefore the question 

 of the activity of the chloroplastids is definitely solved, but as only this 

 one species had been used, further experiments were made with other 

 plants. A modification of Overton's method was employed; portions, 

 20 x 20 mm. square, were cut out from the leaves and floated upside 

 down on the solutions in glass dishes, and in this way free transpiration 

 and respiration could go on through the stomata. The solutions were 

 also changed from time to time, and the edges of the leaves freshly 

 cut. Cane sugar only was used of 5-10 % concentration. The following 

 results were obtained. 



Oplismenus imbecillis. The leaves are variegated red, green and 

 white. In the white portions there are no chloroplastids, not even 

 in guard cells of the stomata. When white portions were used, antho- 

 cyanin appeared in quantity in the epidermis after four days. In the 

 dark, however, there was only slight, though definite, coloration. 

 Hence Gertz concluded that, though not absolutely necessary, light is 



