

326 REV. 0. HENSL0W 02* THE ABSORPTION OF BAIN 



11. On the Preservation of Cat Flowers. 

 Sachs, in his ' Text-book of Botany/ quotes the results obtained 

 by Dr. Hugo de Vries on the withering of plants as follows*: 



"If rapidly growing shoots of large-leaved plants are cut off at their 

 lower part which has become completely lignified, and are placed with the 

 cut surface in water, they remain for some time perfectly fresh. But if 

 they are cut through at the younger parts of the stem and are then placed 

 in water, they soon begin to wither, and the more rapidly and completely 

 the younger and less lignified the part where the section is made. This 

 withering can be easily prevented by making the section under water, and 

 taking care that the cut surface does not come into contact with the air, 

 the conduction of the water through the stem then suffering no interrup- 

 tion, If care is taken that while the section is being made in the air the 

 leaves and upper parts of the stem lose only a very small quantity of water 

 by evaporation, withering does not begin till later, and increases only slowly 

 after the cut surface is placed in water, and the leaves again transpire." 



The cause of withering, Sachs then observes, is the interruption 

 in the conduction of water from below. This agrees with Pril- 

 lieux's observationsf , that as soon as transpiration was checked 

 in a faded shoot by placing it in a humid atmosphere, the water 

 held in reserve in the stalk was drawn upon, and the shoot re- 

 covered. Similarly, Duchartre shows that withering results from 

 one of tw r o causes— -either that the soil may not contain sufficient 

 moisture to balance the loss by transpiration ; or else the latter 

 may proceed more rapidly than the water can be passed up the 

 stem to keep pace with it, and so fail to retain the tissues in their 

 normal state of turgescence. 



Sachs and other observers, however, all allude to the cut end as 

 alone being the place by which water is absorbed ; and as its con- 

 ductivity is rapidly impaired by exposure to air, it is recommended 

 that a sufficiently long piece of the stem should be removed by a 

 new r cut above the first, but this time beneath the surface of the water. 

 For a shoot about 8 inches long, 2 or 2| inches should be cut off. 



Wow Bonnet's experiments and my own clearly show that ab- 

 sorption can take place through the surface of herbaceous stems 

 and by leaves as well as the cut ends. This fact led me to pre- 

 sume that it would be judicious to retain one or more leaves upon 

 a flower-stalk, as well as to allow the stalk itself to be of consider- 



* P. 606, Eng. ed. 



t M Experiences sur la fanaison des Plantes," Couiptes Rendus, tome lxxi. 



p. 80, 1870, 



