124 
OTIS F. CURTIS 
proved, that water moves through the walls by imbibition. Though his 
conclusions are of little value, his data at least suggest that solutes are not 
necessarily carried by the "transpiration stream." 
It will be necessary to conduct experiments using rooted plants and 
various non-toxic salt solutions before any very definite conclusions can 
be drawn as to the region of transfer of salts in plants. 
Summary 
Defoliated stems from which a ring of tissue extending to the cambium 
is removed cease to continue growth. 
This cessation is due to the inability of the xylem to carry the necessary 
food. 
This food is needed not only to supply energy and building material but 
also to increase the osmotic concentration of the tissues, thereby enabling 
them to absorb water. 
This food consists, at least partially, of carbohydrates. 
If the stem above a ring is not defoliated, the leaves are able to supply 
sufficient of this food to allow for considerable growth. 
When dormant stems are ringed, the growth above the rings ceases soon 
after the starch supply is depleted, and the greater the supply of starch 
above a ring the longer will growth continue. 
The carbohydrates stored in the xylem below the ring can not be removed 
through the xylem but must be transferred radially to the phloem, where 
they may be carried downward if there is no second ring below. 
The carbohydrates of the xylem between two rings remain there at least 
for some time after those above the upper ring and those below the lower 
ring have been mostly removed. 
Although large amounts of carbohydrates are stored in xylem tissues, 
there is no appreciable longitudinal transfer of sugars through these tissues. 
Laboratory of Plant Physiology, 
Cornell University 
LITERATURE CITED 
Atkins, M. B. G. 1916. The function of the wood. In " Some recent researches in plant 
physiology," pp. 186-215. 
Bokomy, T. 1890. Die Wege des Transpirationsstromes in der Pflanze. Jahrb. Wiss. 
Bot. 21: 469-503. 
Chandler, W. H. 1914. Sap studies with horticultural plants. Mo. Agr. Exp, Sta. 
Research Bull. 14: 491-552. 
Curtis, O. F. 1918. Stimulation of root growth in cuttings by treatment with chemical 
compounds. Cornell Agr. Exp. Sta. Mem. 14: 71-138. 
Fischer, A. 1891. Beitrage zur Physiologie der Holzgewachse. Jahrb. Wiss. Bot. 22: 
73-160. 
Hanstein, J. 1 860. Versuche iiber die Leitung des Saftes durch die Rinde und Folgerungen 
daraus. Jahrb. Wiss. Bot. 2: 393-467- 
Hartig, T. 1858. Uber die Bewegung des Saftes in den Holzpflanzen. Bot. Zeit. 16: 
329-335, 337-342. 
Kiesselbach, T. A. 191 6. Transpiration as a factor in crop production. Nebr. Agr. Exp. 
Sta. Research Bull. 6. pp. 214. 
