7S7 



To ray knowledge this hypothesis lias not yet been substantiated 

 by ex|)erimenls, so that it seems expedient to reconsider tlie question 

 along what way tiie carbohydrates and the proteins are transported 

 in plants. 



The question can be approached from different sides; in this 

 paper 1 will conline myself to a discussion of some experiments 

 with ringed branches of variegated i)lant8. 



Similar experiments have been made repeatedly with gi'een 

 branches, but then the trouble is that after the buds have opened 

 out, the younger parts above the ring begin to assimilate. 



Stripping olf the leaves or moving the plant to a dark space in- 

 volves otiiei' dilliculties; with variegated shoots it is much easiei' to 

 state any sup()ly of organic matter. 



in <'on.sideratiou of Dixon's hypothesis due precautions should be 

 used in the ringing and the |»roleclion of the injured part. A coating of 

 melted butter of cocoa ] deem more effectual than one of paraffin. It was 

 applied to the wound at a tenq)eratnro of o2° — 33° C. and can 

 hardly injure the exposed surface, as it does not penetrate into the 

 intact cells. ') Moreover, it soon congeals and then affords sufficient 

 protection against outside influences. The parts wei'e then screened 

 from immediate elTect of the sun's rays in oi'der to prevent melting. 



We performed our experiments with variegated branches of 

 Aesculns hippoeastanum L. and Acer Neguiulo L. The former were 

 derived from a stout specimen, whose green top provided the trunk 

 with abundant food and from this trunk numerous yellow shoots 

 had developed. In about 20 years these shoots attained a length of 

 1 M. and a thickness of 7 — 8 mm. in diameter. The specimen of 

 Acer Negundo was provided at the top with greeu-white variegated 

 leaves and developed fiom the main stem and side brandies perfectly 

 white shoots. In neither specimen did the yellow-white leaves contain 

 any chlorophyl'^). An iodine lest pointed to the absence of starch. 



In the spring experiments the branches were ringed (1 — 2 cm.) 

 just before the buds began to open out and at a distance of 1 — 2dm. 

 below the end-bud. 



Three series of experiments were always made at a time. 



I*'' series: green shoots ringed all round. 



2'"' series variegated (yellow-white) shoots ringed all round. 



3"' series variegated (yellow-white) shoots partially ringed, viz. so 

 as to leave as trip of bark as a connecting link, 2 — 4 ram. in breadth. 



1) R. H. ScHiMDT, Flora Bd. 74. 1891. 

 *) Guard-cells of the stoinata excepted. 



