Atkins and Shkrrard — The Pigments of Fruits. 329 



One cross of interest as regards tlie pigments was that between a plant 

 witli unripe fruits, primrose yellow, ripening to red, and one which was 

 dark green, unripe, and chocolate, ripe. When crossed together they 

 gave all the combinations in F2 except yellow (unripe), chocolate (ripe). 

 For instance, there were all the following : — 

 Unripe. Eipe. 



1. Dark green. Chocolate. 



2. Dark green. Eed. 



3. Green. Chocolate. 



4. Green. Eed. 



5. Pale green. Red. 



6. Pale green. Chocolate. 



7. Yellow. Eed. 



It is not the intention of the authors to treat the genetics more fully 

 in the present paper, as enough has been said to elucidate the reasons for 

 undertaking the study of the pigments. 



Microscopic Examination of the Epidermal and Hypodermal Cells of 

 Capsicum Fruits. 



As before mentioned, the colours are due to plastid pigments, almost 

 entirely or wholly so. These are contained in both the epidermis and in 

 the deeper tissues. The difference between the dark green, green, and light 

 green fruits appears to be that in the first-mentioned the cells are smaller 

 and more densely packed with chromatophores than in the two other 

 cases. In the former the cell- walls also are seen to be less thickened. Certain 

 differences in the shade of red which appears in the fruits may also be 

 explained in this manner. The thickening of the walls of tlie epidermal 

 cells is very remarkable. Numerous pits serve to connect the cells. These 

 may be brought out clearly by treatment of a section with a dilute alcoholic 

 solution of benzidine or a-naphthol, with subsequent addition of water and 

 a few drops of neutral three-volume hydrogen peroxide. The reagents are 

 acted upon by oxidases present in the cells, with the production of a deep 

 brown or purple colour, according as benzidine or a-naphthol is employed. 



The red fruits contain brilliant red plastids and a colourless cell-sap. In 

 one case a cell was observed in which the plastids were linear and dis- 

 integrating. This cell contained a purple sap, having all the appearance of 

 an anthoeyan pigment. As it was possible that this might give a clue to the 

 production of the darker shades of red, or even of chocolate, a search was 

 made for other similarly coloured cells, but none were ever found. 



The plastids of the chocolate variety appear a deep red under the micro- 



3 g2 



