20 PHYSIOLOGY OF NUTRITION. 



the chlorophyll is similarly disguised by the presence of a brown 

 pigment, as I ascertained as follows. I collected in the neighbour- 

 hood of Cuxhaven a quantity of Fucus vesiculosus, packed it well 

 so as to keep it fresh, and carried out the actual investigation on 

 the next day. The younger parts of the plants were cut off and 

 boiled for a short time in water. After pouring off the brown 

 liquor the tissue of the algae appeared green."* I now rinsed 

 them with cold water, and treated them with alcohol. This 

 quickly assumed a yellowish green colour; it was poured off and 

 replaced by fresh alcohol. In this way we obtain a splendid 

 green chlorophyll solution, which is highly fluorescent. 3 



We treat with alcohol for some time, leaves from the bud of 

 Elodea, leaves of Funaria hygrometrica, or fern prothallia (the 

 two last are specially to be recommended for our purpose). The 

 objects become colourless, and, on microscopic examination, we 

 perceive in the cells the protoplasmic matrix of the chlorophyll 

 bodies freed from pigment. If we treat the preparations with 

 a drop of a dilute aqueous solution of methyl violet, the de- 

 colourized chlorophyll corpuscles become deeply stained. 



1 On the various relations here mentioned, see Strasburger's Practical 

 Botany (Hillhouse). 



2 See Wiesner, Pringsheim's Jahrbiicher, Bd. 8, p. 575. 



3 See Hansen, Arbeiten d. bot. Instituts in Wurzburg, Bd. 2, p. 289. 



6. Chlorophyll. 



In recent years numerous attempts have been made, notably by 

 Sachsse, Hansen and Tschirch, to isolate chlorophyll in a pure 

 condition from green plant structures. These researches, as also 

 the earlier ones of G. Kraus, 1 have shown that chlorophyll is a 

 mixture of two pigments, viz., a blue-green one, cyanophyll, and 

 a yellow one, xanthophyll. We shall not however here go into 

 the details of the recent work, because the results still have more 

 of a phyto-chemical than a physiological interest; and further, 

 because the methods to be employed for isolating more or less 

 pure chlorophyll preparations are of a highly complicated nature, 

 and very tedious. We must, however, consider carefully the 

 investigations of G. Kraus. 



* The brown pigment mentioned is named phycophaein. The red pigment, 

 soluble in water, which, together with chlorophyll, the Florideee contain, is 

 termed phycoerythrin. The blue-green fission alge contain, in addition to 

 chlorophyll, phycocyan. 



