THE UPWARD TRANSLOCATION OF FOODS IN WOODY 
PLANTS. 1. TISSUES CONCERNED IN TRANSLOCATION 
Otis F. Curtis » 
It seems to be very generally believed that in shrubs and trees there is 
storage of organic matter in the lower part of the trunk and in the roots, 
and that, as growth starts in the spring, this food becomes soluble and 
passes upward through the xylem to the developing shoots and leaves. 
The fact that has been most commonly offered as proof of upward trans- 
location through the xylem is that the xylem tissues of woody plants com- 
monly contain quantities of organic storage products, particularly sugars 
and starches. It has been shown by Atkins (1916), Fischer (1891), and 
others that not only the living parenchyma cells but also the water-con- 
ducting cells proper, the tracheae and tracheids, contain appreciable 
quantities of soluble carbohydrates, and Atkins has found these to be present 
at all seasons of the year. The latter considers that sugars are commonly 
carried through the xylem. He even goes so far as to say that . . the 
transference of carbohydrates can no longer be regarded as an occasional 
and accessory function of the vessels, but is certainly a continual and princi- 
pal function . . . ." It may well be, however, that there is no flow of 
solution through the xylem for any great distance, for a possible frequent 
interposition of living cells across the water-conducting tissues may prevent 
such a flow. Atkins himself clearly recognizes that water may flow across 
tissues containing a high solute content without carrying the solutes with it. 
Experiments performed by Hartig (1858) are also commonly cited in 
texts as offering proof of upward translocation through the xylem. Hartig 
ringed a number of trees early in the summer and found early in the following 
spring that the starch stored below the ring had disappeared. He concluded 
that the storage products must have been translocated upward through 
the xylem. It might be, however, that the food stored below the ring was 
used locally for growth in diameter, or that it was translocated downward 
through the phloem and was used in root growth. 
In order to determine more definitely whether the upward translocation 
of food takes place primarily through the phloem or through the xylem, 
the writer has conducted a series of experiments part of which are reported 
in this paper. Some of these experiments also throw light on the matter 
of food movement from roots or trunks to growing shoots. The discussion 
therefore naturally falls into two main parts: (i) When upward translocation 
of organic matter takes place, as it certainly must for at least short distances, 
does it take place through the water-conducting tissues, the xylem, or 
lOI 
