algae, completely agrees in chemical and physical properties with 
the carotin from the root of Daucus Carota. 
The most recent macrochemical investigations of carotinoids, namely 
that by Wirusrärrer and his pupils have not confirmed Tammrs’ 
results. Wi.istitrER and Mine’) isolated two carotinoids from the 
leaves of the stinging nettle, namely, carotin (C,,H,,) which substance 
was found to be identical with the carotin from the root of Daucus 
Carota and xanthophyll (C,,H,;,O,), whilst WiLLsrärrer and Escuer ®) 
obtain from tomatoes another carotinoid, lycopin (C,,H,,) isomeric 
with Daucus-carotin. From two objects three different carotinoids 
were thus obtained, namely, two hydrocarbons and one oxygenated 
substance. 
The great difference between the results of microscopical and 
macro-chemical investigations determined me to try various methods 
which have been recommended for the demonstration of carotinoids 
by microscopical means. 
These methods are sometimes divided into direct and indirect ones. 
The direct ones depend on the addition of reagents which bring about 
colorations, such as, for example, the beautiful blue coloration with 
sulphuric acid; the indirect methods are based on the separation of 
the carotinoids in crystalline form in the cells or tissues. Only in a 
few cases do the carotinoids occur as crystals in the cells; generally 
they are combined with, or dissolved in a substance that is fluid, 
fatty and saponifiable by alkalies’). This substance occurs in the 
40 
plastids, or forms, as in the case of lower organisms, oily drops in 
the cells *). The aim of the indireet methods is to free the carotinoids 
and to crystallize them out. The following methods belong to this 
category. 
Potash Method. 
This method invented by Mortsen*) was used originally for the 
demonstration of xanthophyll or carotin in green leaves. Fresh leaves 
DR. WitisrArrer, Untersuchungen über Chlorophyll, IV. Ricnarp Wiisrarrer 
und Watrer Misc, Uber die gelben Begleiter des Chlorophylis, Justus Liebig's 
Annalen der Chemie, 355. Bd. 1907, p. 1. 
2) Ricard Wruusrärrer und Heinr. H. Escuer, Uber den Farbstoff der Tomate, 
Hoppe-Seyler’s Zeitschrift für Physiol. Chemie, 64. Bd. 1910, p. 47. 
5) I. G. Kour, Untersuchungen über das Carotin und seine physiol. Bedeutung 
in der Pflanze, 1902, p. 118 et seq. 
*) W. Zoer, Zur Kenntnis der Wärbungsursachen niederer Organismen, Erste 
Mitteilung, Beiträge zur Physiol. und Morphol. niederer Organismen, Erstes Heft, 
1892, p. 35. Zweite Mitteilung, |. c. Zweites Heft, 1892, p. 5. ; 
5) Hays Mouiscu, Die Krystallisation und der Nachweis des Xanthophylls (Caro- 
tins) im Blatte, Ber. d. d. bot. Ges. Bd. XIV, 1896, p. 19. 
