844 SEC. 18. BIOLOGY. 



3936. Apparatus for demonstrating Knight's Experi- 

 ment on the influence of gravity on the direction of the growth 

 of roots and stems of budding plants. (Exhibitor's construction.) 



Prof. Dr. F. Cohn, of the Institute of Vegetable Phy- 

 siology in the University of Breslau. 



Some seeds (by preference Pisum sativum and Zea mays) are soaked for 24 

 hours in water, and then attached by long needles, which must not pass through 

 the radicle or the plumula, but only through the cotyledons or the endosperm, 

 radially to the circumference of a disc of cork. The apparatus is set in action 

 by connecting the caoutchouc tube of the cover with the water supply or a 

 water reservoir. By regulating the strength of the stream of water the rate 

 of the waterwheel can be increased or diminished. The splashing of the water 

 furnishes sufficient moisture for the germination of the seeds, so that all the 

 roots are developed centrifugally, whilst the stems grow in a centripetal 

 direction. An apparatus similar to this was employed by Prof. Ciesieboki in 

 the Institute of Vegetable Physiology for his researches on the bending down- 

 wards of the root (see Cohn's Beitrage zur Biologic der Pflanzen, Vol. I., 

 part 2). The observations can be made through the glass window, which is, 

 however, generally closed by a shutter in order to keep out the light. 



3937. Apparatus for Observing the Velocity of Growth 

 in Plants (constructed by Prof. Beincke). 



Institute of Vegetable Physiology of Gottingen, Director 

 Prof. Griscbach. 



3938. Apparatus for Registering the Growth of Plants. 



E. Stohrer, Leipzig. 



The principle of the apparatus is, that the making and breaking of a 

 galvanic current sets in motion a vibration which works between the poles 

 of an electro-magnet, and carries a writing point at its extremity. This pen 

 is pressed against and marks on a drum of paper (which is turned round 

 once in 24 hours by clockwork) a circular line. The portion of the plant 

 under observation is brought into connexion with the pen by means of a 

 delicate system of levers. A growth of even ^ 1 millimetre of the plant 

 will cause the making and breaking of the current to be attracted and released, 

 the vibrator will thus move, and on the circular line will be recorded curved 

 tracings which indicate the growth of the plant. 



The second registering apparatus of which only a photograph is sent is 

 intended for researches on transjection and the pressure exerted by the root. 

 A sheet of paper divided into minutes and hours is applied to a large brass 

 cylinder, which is turned round on its axis daily or hourly by clockwork. 

 The oscillations of the column of water are written on the paper by means of 

 a cork float bearing a glass pen filled with anilin solution. 



3939. Apparatus for Researches on the Physiological 

 exchange of Material in the Sheep. 



Prof. Henneberg, Agricultural Research Office, Station of 

 the Hanoverian Agricultural Society, Gottingcn. 



It is necessary for researches on the total exchange of material in mi 

 animal to collect completely and separately the feces and the urine. The 

 stall exhibited serves to illustrate the method in which the experiment was 

 carried out at the Research Station at Gottingen-Weende, when a sheep 

 formed the subject of investigation. The single pen stall was erected in the 



