604 Physiologie. 



einen reduzierenden Zucker (vielleicht Glukose). Aus dem Ueber- 

 schusse der entstandenen Glukose ist zu schliessen, dass neben des 

 erwähnten Glukosides die Pflanze noch ein anderes (bisher noch 

 nicht studiertes) Glukosid enthält. Matouschek (Wien). 



Brown, A. J., The selective permeability of the cove- 

 rings of the seeds of Hordearn vulgare. (Proc. Roy. Soc, Se- 

 ries B, Vol. 81, N°. B. 546. p. 82—93. 1909.) 



The author has continued his researches on the selective permea- 

 bility of the seed-coat of barley. This discovery of the existence 

 of a natural dead semipermeable membrane is at present unique. 

 The semipermeability seems to reside in that layer of the confluent 

 walls of the grain which is derived from the epidermis of the nucellus. 



In previous work the blue pigment in the endosperm of this 

 variety of barley furnished evidence that mineral acids were kept 

 out while water freely permeatecl. Now the test for permeability 

 applied is the gain in weight of the grain by the intake of water. 

 If barley is immersed in a normal Solution of a salt to which it is 

 quite impermeable then there is competition for the water available 

 between the starch and other colloids of the grain which imbibe 

 water and the osmotic force of the dissolved salt outside the grain. 

 In such a case the seed cannot imbibe its füll weight of water (70°/ ) 

 and the gain of weight may be only 40% when equilibrium is 

 attained. If the substance dissolved in the outside water permeates 

 the membrane of the grain readily then there is no such Opposition 

 and the solute and the solvent pass through together and the seed 

 imbibes its maximum amount of water. 



Test of selective permeability made in this way show that mer- 

 curic Chloride and Cyanide pass through but other mercury salts are 

 kept out. Mineral acids cannot pass but formic and acetic acid pass 

 freely, glycellic and lactic only after some time. Trichloracetic acid , 

 though a strong electrolyte. passes through freely and so does 

 ammonia in dilute Solutions. 



Among non-electrolytes, alcool ethylaldehyde and acetone pass 

 freely but glycine, glycerol and sugars do not pass. 



The property of passing this semi-permeable membrane does 

 not seem to be correlatable with any recognized physical property, 

 neither with dissociation, surface tension nor viscosity. It is hypothe- 

 cated that it depends on some peculiarity in the way the molecules 

 of these two classes of substances are combined respectively with 

 the water molecules of the solvent. J. J. Blackman. 



Dachnowski, A., Bog toxins and their effects upon soils. 

 (Bot. Gaz. XL VII. p. 389—405. flg. 1-2 My. 1909.) 



The available Information, from the study here reported, may 

 be summarized as follows: 



1. Many swamp and muck soils exhibit a sterility which cannot 

 be remedied by drainage or by the addition of fertilizers. 



2. The sterility appears to be most marked where investigations 

 on the physiological properties of bog water and bog soils indicate 

 a greater amount and activity of bog toxins. 



3. The production of bogs toxins is due to a number'of physical 

 and chemical factors. One can only conclude that the chemical Con- 

 stitution of bog water and bog soils at a given moment conditions 



