126 Experimentelle Morphologie, Transplantation. 



319) Hiley, W. E., On the value of differeut degrees of centrifugal 

 force as geotropic Stimuli. In: Annais of Botanv, Bd. 27, S. 719 — 758^ 

 Figs. 3, PI. 57—58, 1913. 



The author reviews the previous work on the use of centrifugal wheels in 

 the study of geotropic responses. He treats the subject mathematically, giving 

 methods of measuring centrifugal force, and describes a large number of experi- 

 nients in which a specially constructed intermittent centrifuge was used, in which 

 the organ is alternately subjected to Stimulation from centrifugal force and from 

 gravitation. He finds that the stimulating force multiplied by the time of action 

 must be the same in each direction if a radicle is to remain straight under the 



CT 

 infiuence of two opposing alternating Stimuli • j=l. But this equation does 



not hold if the total periods of Stimulation are too long. When the time bet- 

 ween two intermittent movements was as much as 20 minutes, it was necessary 

 for the centrifugal force to act for a longer time in order to produce the same 

 effect. This is probably because the radicle may respond negatively to too long 

 exposure to centrifugal force. 



The presentation time for Helianthus radicles was found to be 3 — 4Y2 mi- 

 nutes at a temperature of 18^ — 20*^0. It is finally concluded that "in any given 

 radicle a constant amount of response takes place to a Stimulus of a given num- 

 ber of mg. sec. Units, however this number may be made up, so long as the time 

 of exposure to the Stimulus is not long". Gates. 



320) Harper, Alan Gr., Defoliation: its effects upon the growth and 

 structure of the wood of Larix. In: Annais of Botany, Bd. 27, S. 621 — 

 642, Fig. 2, PI. 49—50, 1913. 



The writer studied material of larch-w^ood from trees which had been pre- 

 maturely defoliated in the English Lake District, by attacks of the larch sawfly. 

 He finds that premature defoliation results in a certain degree of starvation of 

 the trees, and starvation affects both the quantity of growth and the structure 

 of the wood formed. In severe starvation, the activity of the cambium is sus- 

 pended in certain regions, particularly towards the base of the tree and in 

 limited areas of the circumference. The first effect noted is a reduction in the 

 thickening of the walls of the xylem cells in the autumn wood. These cells are 

 also often smaller than their usual size. Gates. 



321) Heimaun, Fritz, Über Röntgentiefeutherapie. In: Berliner Klinik,. 

 Heft 301, S. 10, 1913. 



Bei der Behandlung mit Röntgenstrahlen, die in der Medizin mehr und mehr Be- 

 deutung gewinnt, werden heute von manchen Seiten bereits über 1000 X in einer Sitzung- 

 verabreicht. Verf. beschreibt die Einrichtung der Breslauer Klinik. Neben dem 

 Rekord- und dem Wehnelt- Unterbrecher ist noch der sog. Rythmeur angeschafft 

 worden, der den Primärstrom nur 100 — 200 mal pro Minute unterbricht und so eine 

 allzustarke Erhitzung der Antikathode vermeidet. Als Röhren dienen die Müller- 

 schen Wasserkühlröhrchen oder die von Gundelach mit Metallkühlung hergestellten 

 Röhren. Die Stärke der für die Tiefentherapie verwendeten Röhren beträgt 9,5 — 11 Wh. 

 Sie wird mit dem Wehneltschen Kryptoradiometer abgelesen. Die Belastung betrug 

 in der letzten Zeit Ty^ M.-A. Als Dosimeter benützt man das Quantimeter von Kien- 

 böck und die Tabletten von Saboureaud und Noixe. 



Durch die Untersuchungen von Gauß, Meyer, Hoffmann u. a. ist er- 

 wiesen worden, daß gefilterte Strahlen sowohl an Tiefenwirkung als auch an biolo- 

 gischem Effekt die ungefilterten Strahlen übertreffen, ferner werden durch Ab- 

 fangen der weichen Strahlen Hautschädigungen vermieden. Es wird mit Alumi- 



