WEEPING OF THE ROOT-STOCK. 



371 



into the hollow of the stem. This contains sugar and albuminous substances, and 

 therefore passes over into alcoholic fermentation ; and, according to the statement of 

 Alexander von Humboldt, hundreds of litres of sap may be gradually obtained in 

 this manner from a single plant. It was formerly believed to be a special peculiarity 

 of some few plants thus to expel the water absorbed by the roots at the transverse section 

 of the stem, until Hofmeister showed (about 1850) that the same phenomenon may 

 be observed in any given plant, even small annuals which form little wood; it is 

 only necessary to cut off the stems of Ricinus, Tobacco, Digitalis, Nettle, Sunflower, 

 Maize, and such like well-known cultivated plants above the roots, when they are 

 already actively vegetating, and to connect 

 a glass tube at the section of the stem, to 

 observe most of the phenomena referred to ; 

 and this may be done the more conveniently 

 since even plants cultivated in flower-pots 

 are suitable for the purpose. Such an 

 experiment proceeds best and simplest if 

 the plant is allowed to grow, not in soil, 

 but in an aqueous solution of nutritive sub- 

 stances (Fig. 210), until it has developed a 

 vigorous root-system ; the stem is then cut 

 off, and the root-stock connected with an 

 exit-tube, and as the roots absorb water 

 from the nutritive fluid, an equal quantity 

 exudes above at the transverse section of 

 the stock. 



The weeping of the root-stock has, 

 since the time of Hales (1721), been in- 

 vestigated a thousand times by the most 

 various observers, and it would require 

 many hours to refer to all the results in 

 detail. Instead of this, however, we will 

 commence our further considerations on 

 the phenomenon in question with a definite 

 example. In August, 1881, a very vigor- 

 ous specimen of the Sun-flower (Helianthus 

 annuus), about 3 metres high and with a 

 stem 4-5 centimetres in diameter, which 



was growing in the open land in my experimental garden, and was thus quite 

 normal, was cut off transversely about twenty-five centimetres above the sur- 

 face of the earth, and an appropriate exit-tube at once placed on the stump of 

 the stem; the descending curved limb of the latter allowed the water expelled 

 from the root-stock to pass into a graduated cylinder. Since the experiment 

 was commenced on a hot day, the following phenomenon, to which I shall 

 return below, presented itself: the root-stock, instead of expelling water at once, 

 on the contrary absorbed a not inconsiderable quantity of water through the trans- 

 verse section of the stem during the first few hours. The outflow from the section 



Fig. 210, — A Maize plant developed in a nutritive solution 

 in the vessel a, is cut off above the cork {b) at c, and here con- 

 nected with the glass tube efg by means of caoutchouc (rf). 

 The narrow glass tube h passes through the cork g: esh is 

 filled with water, and mercury is then poured in h. This 

 mercury is driven up by the water expelled from f, as shown at 

 I and k. 



