METABOLIC PROCESSES IX THE PLANT. '351 



the later spring. The solution begins in the young branches, 

 so that these rapidly (perhaps in the course of fourteen days) 

 become free from starch both in the cortex and wood ; later it is 

 exhibited in the older branches also. A good object for investi- 

 gation is Betula. 



AVhen the leaves have at last completely unfolded, so that large 

 quantities of carbohydrates are produced, these gradually travel 

 in larger and larger quantities into the stem structures, a process 

 which must naturally be very essentially influenced by the charac- 

 ter of the weather. Finally the autumnal starch maximum is 

 reached of which we spoke above. 



\Vo make still further the following interesting experiment, in 

 order to show that the process of reconversion of starch from fat 

 or glucose, in the branches of our trees, is very essentially depen- 

 dent on the temperature to which they are exposed. In winter, 

 at the time of the starch minimum, i.e. in December or January, 

 a bough is cut down from a lime tree, brought into the warm 

 room, and left there with its lower end in water. The regenera- 

 tion of starch begins after a few days, and continues. 



1 See A. Fischer, Jahrbiicher f. wissensclil. Botanik, Bd. 22. 



141. Kinging Experiments. 



For ringing experiments willow shoots are especially suitable. 

 It is best to make the observations in spring, and I obtained par- 

 ticularly good results in investigations with Sali$ ragilis. The /^ 

 willow shoots, about 200 mm. long and 12 mm. thick, are ringed 

 at their morphologically lower end, the process consisting in the 

 removal of a ring of cortex about 20 mm. broad at a distance of 

 say 40 mm. from the bottom, so that at this place the wood is laid 

 bare. The branch is now suspended in a sufficiently tall glass 

 cylinder by twisting a thread round its upper end, and fastening 

 the thread by means of sealing-wax to a glass plate closing the 

 mouth of the cylinder. The bottom of the cylinder is covered to 

 a depth of a few millimetres with water, into which however the 

 shoots must not be allowed to dip. Moistened strips of blotting- 

 paper, lining the inner side of the cylinder, materially assist in 

 keeping the air in it uniformly moist. In an investigation which 

 I made, a ringed willow branch was left in a glass cylinder in the 

 dark from March 19th till April 21st. The result of the experi- 



