METABOLIC PROCESSES Itf THE PLANT. 355 



following experiment. At the end of January we cut a Syringa 

 shoot provided with two one-year-old branches, put it with its 

 base in water, and ring it just below the point at which it forks. 

 In the warm room the buds unfold in the course of a fortnight 

 or three weeks. The wood laid bare is to be covered with graft- 

 ing wax. At the commencement of the experiment the wood 

 of the twig contains much starch. When the buds have unfolded, 

 the starch has almost completely disappeared, not only from the 

 branches, but also from the wood at the level of the ring, and 

 from the wood of the two-year-old portion of the branch below 

 the ring. The substance of the starch has been sent upwards in 

 the vessels of the xylem in the form of glucose. 



1 Literature : Hanstein in Pringsheim's Jahrbiicher, Bd. 2 ; Sachs, Flora, 

 1803, p. 33. 



2 See A. Fischer, Jahrbiicher, Bd. 22, pp. 137 and 142. 



142. The Starch and Sugar Sheaths and their Functions in 

 Connection with Translocation. 



Many plants are characterised by the possession of a starch 

 sheath, and we may conveniently observe such a sheath if we 

 prepare transverse sections from the stems of, e.g., bean plants, 

 which have developed in darkness till the first internode has 

 elongated considerably. Epidermis, cortex, pith, and vascular 

 bundles are easily distinguished. The circle of vascular bundles 

 is surrounded on the outside, i.e. on the bast side; by a layer 

 of cells whose elements are smaller than those of the cortex, and 

 this is the starch sheath. We find large quantities of starch in 

 the cells of this bundle sheath, a fact which has led to the 

 conclusion that the translocation of carbohydrates takes place 

 especially in the starch sheath. Nevertheless, various facts are 

 not in unison with such a view. We prepare in July transverse 

 sections from the lower part of the stem of a vigorous plant of 

 Phaseolus grown in the open. Each vascular bundle is furnished 

 on the outside with a strongly developed layer of bast fibres, and 

 we can easily make out, by microscopic examination, that large 

 quantities of starch are present in the parenchyma both of cortex 

 and pith. The cells of the starch sheath, on the other hand, are, 

 as I have satisfied myself, very poor in starch, or contain 110 

 starch grains at all. From this it follows that translocation of 



