CURRENT LITERATURE 
BOOK REVIEWS 
Rhythm, periodicity, and zonation 
Kister’s booklet! on zone formation in colloidal media contributes little 
if anything to botany as such, but is well worth while in presenting a point of 
view held by a number of continental workers. The first chapter (pp. 23) 
deals with equidistant zones, the second (pp. 41) with breaks, dislocations, 
etc., in the zones, the third (pp. 32) with excentric ring systems and polycentric 
diffusion fields, and the fourth (pp. 7) with zoological considerations and dis- 
cussion. His point of departure is the Liesegang rings. The concentric rings 
are produced in a few hours after placing a droplet of 80 per cent AgNO; on 
5-10 per cent gelatin plate bearing 0.1 per cent K,Cr,O;. The rings consist 
of Ag,CrO, and become more definite and more distant from each other as 
the distance from the drop increases. The author mentions OsTWALD’S 
explanation of the Liesegang rings on the basis of zones of stable, metastable, 
and labile concentrations; also the fact that the explanation has been ques- 
tioned. 
The bands formed in capillary tubes show definite rhythm and polarity. 
Aside from the Ag,CrO, bands, there are others caused by impurities in the 
gelatin which Ktster terms small thythms, in contrast to the great rhythms 
of Ag.CrO,. Many conditions modify the patterns given by the precipitate 
of Ag.CrO,: contact with the dish in contrast to free gelatin, presence of 
foreign bodies in the gelatin, tensions and pressures, and others. In fact, 
patterns can be produced that resemble closely all the various patterns appear- 
— mm mottled leaves, in the arrangement of vascular elements of plants, and 
in markings of tracheae. 
The writer emphasizes the fact that the pattern differentiation of Ag.CrO, 
precipitate shown in the gelatin plate is a self-differentiation occurring under 
polarized 
complex 

rt F, 
iitiiecms in kolloidalen Medien. Beitrage 2ur 
ischen Anatomie des Pflanz . XfIll. 
8S. 53. Jena: Gustav Fischer. 1913. hc Agden 
230 


