1032 SUMMARY OF CURBENT RESEARCHES RELATESTG TO 



10 m., at least when the pressure of the air which surrounds the wood 

 of the roots is not greater than the atmospheric pressure. It is pos- 

 sible that columns of water may be formed which are interrupted 

 only by saturated walls ; but these, if they are long enough, will soon 

 become immobile, and will play the part of the columns found in the 

 vessels. They are besides of small constancy, because the active 

 absorption of water by the surrounding elements breaks them up, or 

 because they are themselves displaced by sinking. 



Galvanotropism.* — Herr L. Eischawi gives a resume of all the 

 previous observations on this subject ; and has repeated the experi- 

 ments on seedlings of Yicia Faha by means of Du Bois Eeymond's 

 apparatus. A positive curvature is easily obtained, which he explains 

 in this way, that, under the influence of a galvanic current, the water 

 in the root moves in the direction of the current. In consequence of 

 this the turgidity of the cells increases on the side facing the cathode, 

 which therefore elongates and causes a positive curvature. Negative 

 and S-shaped curvatures stated to occur with a very weak current, 

 the author found it very difficult to obtain ; and, when obtained, they 

 very soon became obliterated, and gave place to positive curvatures. 

 They may be explained by assuming that with a weak cm'rent a slight 

 diffusion is at first caused of the external fluid into the cells, espe- 

 cially on the side facing the anode, in consequence of which this side 

 elongates, causing a negative curvature. 



Transpiration-currents.t — Dr. A. Hansen describes experiments 

 on living plants which tend to confirm his previous theory that 

 transpiration-currents are due to imbibition. All the experiments 

 negative the possibility of root-pressure taking any part in the pheno- 

 menon ; the plants experimented on remained fresh for days, and 

 absorbed considerable quantities of water through dead roots. They 

 are equally opposed to Godlewski's hypothesis that osmose performs 

 an essential part in causing the transpiration-currents. 



Absorption by the Plant of Non-nutrient Substances.^ — HerrW. 

 Knop describes a series of experiments for the purpose of determining 

 the effect on plants of supplying to the soil in which they grow dilute 

 solutions of various mineral salts. The degree is stated in which each 

 ingredient was absorbed, and in which it produced a poisonous effect 

 on the plant. 



B. CRYPTOGAMIA. 



Cryptogamia Vascularia. 



Bursting of the Sporangium of Ferns and the Anther of Flower- 

 ing Plantr.l — Herr J. Schrodt reviews the existing literature of this 

 subject, and gives the results of his own observations made with the 

 assistance of the camera. In the case of Scolopendrium vulgare, the 

 movements of the annulus, resulting from alternations of dryness and 



* Bot. Centralbl., xxii. (1885) pp. 121-6. 



t Arbeit. Bot. Inst. Wurzburg, iii. (1885) pp. 305-14. 



t Ber. Verhandl. K. Sachs. Gesell. Wiss., 1885, pp. 39-54. 



I Flora, Ixviii. (1885) pp. 455-67, 471-99 (1 pi.). 



II 



