500 BOTANICAL GAZETTE [DECEMBER 
are absorbed by the stroma, i. e., held mechanically by molecular affinity, and 
in different degrees under different conditions, this molecular attraction being 
overcome by the various solvents unequally. Consequently, it is argued, the 
pigments cannot exist as grana in the stroma—a conclusion already indicated 
by recent study both with microscope and ultramicroscope. Many bodies 
beside cellulose hold the pigments in like fashion. The work is suggestive, but 
SWETT’s crucial experiment is not convincing. 
Inasmuch as the different pigments are held fast unequally, if a petrolether 
solution, or even better a solution in carbon bisulfid, be filtered through a column 
of calcium carbonate, the pigments are distributed in zones, the more firml 
adsorbed ones above, the less firmly fixed successively lower. Such a preparation 
he calls a chromatogram, and the method the chromatographic method.?" 
In a later paper?? Tswett gives further details of the technique and analyzes 
the zones of his chromatogram. The synonymy of the chlorophyll pigments is 
so tangled that it is almost impossible to compare the work of different investi- 
gators. The chromatographic method promises to be of use in demonstrating 
that there are different pigments, but its value in research seems questionable. 
—C.R.B 
The Svalof Experiment Station.—Although the work of the Swedish Agri- 
cultural Experiment Station at Svaléf is widely celebrated because of its note- 
worthy economic results, these results and the means by which they have been 
attained are not generally understood, owing to the fact that all of its reports are 
printed in the Swedish language. Dr Vrres has devoted two recent papers?3 to a 
discussion of the Svaléf methods and their scientific significance. In the first 
of these papers is given a brief history of the station, together with an exposition 
of the methods employed. The history of the station falls rather naturally 
into four 5-year periods, each marked by a characteristic advance. During 
e first period, 1886-1891, the work of introduction and testing of varieties, in 
the way usually done by Agricultural Experiment Stations, presents nothing 
unique, the several sorts being treated as units. With the appointment of Dr. 
H. Nitsson as Director in 1890 begins the second period, in which the discovery 
was made that each variety is a mixture of a large number of elementary forms 
and that the latter are the real units with which scientific agriculture must deal. 
In the third period was carried out the great work of segregating the elementary 
st bt kdaed Propores to call the collective green pigment of leaves chlorophyll; 
green fl ; the yellows already are distinguished 
sefearotins a xanthophylls. 
22 Tswett, M., Adsorptionsanalyse und chromatographische Methode. Anwen- 
oS idie Chemie des Chlorophylls. Ber. Deutsch. Bot. Gesells. 24: 384-393- 
23 ne a Hueco, Die Svaléfer Methode zur Veredelung landwirthschaftlicher 
Kulturgewachse und ihre Bedeu _, fiir die Selektionstheorie. Arch. fiir Rass. u. 
Gesells. tone 3:325-358. My-Je 190 
re und neu capa Meine Biol. Centralbl. 26: 385-395. Jy 1906. 
