Physiologie. 107 



ßordner, J. S., The influence of traction on the for- 

 mation of mechanical tissue in stems. (Bot. Gaz. XLVIII. 

 p. 251—274. 1909) 



After an historical review and an account of the methods used, 

 a number of experiments are described. The results showed that 

 actively growing stems of herbaceous plants [Helianthus, Ricinus, 

 etc.), and Vinca major respond to traction along their longitudinal 

 axes, by increasing their breaking strength; also by an increased 

 development of bast or xylem and in most cases by an increase of 

 both these mechanical tissues. Experiments with Rubiis occidentalis 

 convinced the author that the tension used by Wiedersheim on 

 pendant woodv branches was not sufhcient to send a Stimulus past 

 the Stimulus threshold. Trelease. 



Crocker, W., Longevity ofseeds. (Bot. Gaz. XL VII. p. 69—72. 

 1909.) 

 A criticism. of E wart 's article on the same subject (Reprint 

 Proc. Roy. Soc. Victoria N. S. XXI p. 210. 1908.) Comment is made 

 upon the significance of the seed coats in Crataegus mollis, the 

 relation of high temperature to germination in Xanthium echinatum, 

 the effect of excluding oxygen upon germination, etc. Emphasis is 

 laid upon the conclusion that delayed germination in seeds is 

 generali, though not always related to seed-coat characters, rather 

 than to so-called dormancy of protoplasm. Trelease. 



Czapek, F., Die ßewegungsmechanik der Blattgelenke 

 der Menispermaceen. (Ber. deutsch, bot. Ges. XXVII. 7. 

 p. 404—407. 1909.) 



Verf. untersuchte Anamirta Cocculus und Tinomiscium javanicutn 

 und fand, dass die Bewegung der überaus grossen Blattgelenke 

 geotropischer und heliotropscher Natur sei. Der Krümmungsmecha- 

 nismus besteht in einem ungleichmässigen Wachstum auf den 

 gegenüberliegenden Seiten der Gelenke, ist also keine Variations- 

 bewegung. K. Snell. 



Ganong, W. F., New normal appliances for use in plant 

 physiology. V. (Bot. Gaz. XLVIII. p. 301—305. fig. 1—2. 1909.) 



Space markers, for marking off a structure into regulär divisions, 

 either areas for use with leaves, or lengths, as in roots and stems, — 

 are described. Also a demonstration auxograph, combiningreasonable 

 accurac5^ ready portability, visibility of record for some distance and 

 clear exhibition of its mechanism and principle, is described and 

 figured. Trelease. 



Gräfe, V. und E. Vieser. Untersuchungen über das Ver- 

 halten grüner Pflanzen zu gasförmigem Formaldehyd. 

 (Ber. deutsch, bot. Ges. XXVII. 7. p. 431—446. 1909.) 



Unter einer dichtschliessenden Glasglocke wurden die ober- 

 irdischen Teile einer Reihe von P/zaseo/wsflanzen der Einwirkung 

 von gasförmigen Formaldehyd ausgesetzt und durch titrimetrische 

 Bestimmung und Vergleich mit einem Kontroll versuch das aufge- 

 nommene Formaldehyd bestimmt. Im Allgemeinen wurden maximal 

 0,001 g Formaldehyd pro Pflanze ohne Schädigung aufgenommen. 



