309 
Substance in Indigo-yielding Plants . 
occurs m certain cells where chloroplasts do not occur, e.g. the epidermal 
cells and vascular strands of Isatis (5) ; the blossoms of Echites religiosa 
(17) ; laticiferous vessels of Echites (17), &c. 
It is clear, therefore, that the indigo-forming substance is not located 
only in those cells in which chloroplasts occur ; a fact which the foregoing 
account has made, if possible, more clear. The presence in tissues, other 
than those containing chloroplasts, does not of necessity preclude these 
bodies from taking an active part in the formation of the substance. The 
indigo-forming substance is undoubtedly a soluble body, and retained 
within the cell in a condition of solution. It may, therefore, pass from the 
chloroplast, where it is supposed to be formed, to the various tissues of 
the plant. It becomes necessary, therefore, before any part in the form- 
ation of the indigo-forming substance can be claimed for the chloroplast, 
to prove some definite relation between this and the blue precipitated. 
This can only be done by a minute examination of the distribution of 
indigo within a cell containing chloroplasts. For this purpose the cortical 
cells of a young stem of Strobilanthes is most suitable. Examination 
under a high power (Fig. 16 ) shows the blue distributed throughout 
the plasm of the cell. Here and there a granule may be found deposited 
in contact with a chloroplast, but in no case has it been possible to locate 
the blue within the latter body, as Molisch claims to have done. 
Further, in no case where the deposition of indigo within the cells 
of a chlorophyll-bearing parenchyma has been examined has it been possible 
to trace deposition within the chloroplast. The indigo is, moreover, 
frequently found deposited in contact with the nucleus, and it seems 
impossible to lay greater stress on this contact in the one case than in 
the other. Until further proof, obtained from work along different lines, 
is obtained it is impossible to accredit to the chloroplasts any direct 
function in the production of the indigo -forming substance. 
Literature. 
1. E. Schunck : Phil. Mag. (4), vol. x, p. 74, 1855. On the formation of Indigo Blue, Part I. 
2 - : Phil. Mag. (4), vol. xv, p. 127, 1858. On the formation of Indigo Blue, Part II. 
3 . H. R. Goppert : Bot. Zeit., 29, No. 24, p. 399, 1871. Wann stirbt die durch Frost getodtete 
Pflanze, zur Zeit des Gefrierens oder im Moment des Aufthauens ? 
4 . H. Muller-Thurgau : Landw. Jahrb., ix, pp. 157-166, 1880. Ueber das Gefrieren und 
Erfrieren der Pflanzen. 
5 . H. Molisch : Sitzb. der Kais. Akad. d. Wiss. in Wien. Bd. cii, Abth. 1, p. 269, 1893. Das 
Vorkommen und der Nachweis des Indicans in der Pflanze, nebst Beobachtungen tiber ein 
neues Chromogen. 
