62 Wisconsin Academy of Sciences, Arts , and Letters. 
only about 27 cm. high in January and their stems about 21 mm. 
in circumference, while those in four liter pots were about 90 
cm. high and 50 mm. in circumference. Those transplanted to 
the field became large plants with woody stems. Five dwarfed 
plants, which were subsequently transplanted to a forcing bed, 
had since made a rank growth and were retransplanted to four 
liter pots. They wilted but eventually recovered their turgid- 
ity, although the older leaves died. 
Cross sections showed the xylem cells of the field plants 
to be larger and the vessels more numerous than in those re¬ 
tained in the small pots. In the plants transplanted to the field 
the xylem cells around the pith were small and were surrounded 
by larger ones toward the periphery. In case of those trans¬ 
planted to four liter pots the same inversion of the normal po¬ 
sition of large and small celled xylem occurred, but in addition 
the outermost rows again had a much reduced radial diameter. 
In the field plants which had been retransplanted to pots the 
outermost cells also had a reduced radial diameter and thick 
walls while within them was a zone of large, thin-walled cells 
which had apparently been formed just before the last trans¬ 
planting and as a result their walls remained unthickened. 
Similar results were also obtained with Helianthus annuus. 
Wieler concluded from these experiments that the abundant 
supply of metabolized food to the cambium is the most important 
factor in the production of spring wood and that the shortage 
of such a food supply induces the formation of summer wood, 
and that therefore “annual” rings of trees are due to an abun¬ 
dant supply of organic food to the cambium in spring and a 
reduced supply in summer. 
Lutz 124 was of the opinion that when the food supply to a 
rapidly dividing cambium is comparatively low while water is 
abundant the cells become large and thin-walled as is charac¬ 
teristic of spring wood, while if the food supply is good and the 
water is low the cells become small and thick-walled as in sum¬ 
mer wood. 
In a later paper Wieler 125 reiterated his former conclusions 
though he admits his inability to prove that the small radial 
124 1. c. 
125 Wieler, A. Ueber die Abhangigkeit der Jahresringbildnng von den 
Ernahrungsverhaltnissen. Allgem. Forst-u. Jagd-Zeit. 67: 82-89. 1891. 
