DIE GESTALTS UND LAGEVERANDERUNG 77 
teen per cent., and currents of air for thirty per cent. 
The letterpress is excellent, and the photographs enable one 
vividly to realize the various points treated. Professor Seward an 
the authorities of the Cambridge University Press are heartily to 
be congratulated on the production of this fascinating little book. 
- S. M. 
Die Gestalts und. Lageverdnderung der Pflanzen-Chromatophoren. 
Mit einer Beilage: Die Lightbrechung der lebenden Pflan- 
zenzelle. By Dr. Gustav Senn. With 83 text-figures and 
9 tables. Leipzig: Engelmann. 1908. 
of new facts and observations bearing on these problems. 
With respect to change of form, the author shows that light 
the Mesocarpus, Vaucheria, Chromalina, Eremosphora, Funaria, 
Ground-tissue, and Palisade-parenchya types; and then proceeds 
to describe the characteristic behaviour with respect to light and 
other conditions of these several types. 
- He concludes from his investigations of Mesocarpus that the 
chloroplast in this type of plant is balanced as to position by its 
two-fold reaction: in mid-light it is the red rays which maintain 
the axial plate-like chromatophore in its “ full-face position, viz., 
in a plane at right-angles to the incident light; in high-light 
intensity it is the reaction of the chromatophore to the blue rays 
which swings it through an angle of 90° till the chloroplast reaches 
i fh his experiments with Vaucheria, Dr. Senn 
he numerous small chromatophores to 
light—resulting in their accumulation in the optimally illuminated 
