292 
AMERICAN JOURNAL OF BOTANY 
[Vol. 8 
according to the plant and the particular object in view. In the bean 
seedling cell turgor is somewhat reduced in the cooled region after some 
days, particularly in the lower temperatures. On removal of the coil, 
however, normal turgor is reestablished within a few hours, and if the 
temperature is raised gradually at the end of the experiment the turgor is 
normal when the wrapping is removed. 
In the experiments on Bryophyllum- the low temperature is applied 
to a zone of the petiole 2-3 cm. long, and the leaf is immersed in water so 
far as its position on the plant will permit. The opposite leaf of the same 
node and usually leaves of other nodes above and below are also immersed. 
In the experimental leaf all or nearly all the immersed buds develop, in 
the opposite leaf there is as much or almost as much development in most 
cases, and more or less development occurs in leaves of nodes above and 
below the experimental node. Controls with leaves immersed but without 
the low temperature often show development of a bud here and there, but 
the effect of the low temperature is clear and unmistakable in the experimen- 
tal leaf, in the opposite leaf, and to a less extent in leaves of neighboring 
nodes. 
The case of the scarlet runner bean is of greater interest than that of 
Bryophyllum, for here the low temperature is applied to the main stem of 
the seedling, and all water and nutrition passing to parts above must pass 
this zone. If the low temperature interferes appreciably with the flow 
of fluids, this should be evident in the retardation of growth above the zone, 
or in extreme cases in wilting. There is in some cases slight retardation of 
growth of the tip, particularly when the low temperature is applied to the 
upper part of an internode of the young seedling in which elongation is still 
going on and the vascular bundles are still developing. Except when the 
temperature is very low, however, this retardation is only temporary and 
the rate of growth of the tip increases even before the low temperature is 
removed, and in no case is the effect on the tip sufficient to decrease its 
dominance to such an extent that axillary buds above the low temperature 
zone develop. Morevoer, that this retardation has nothing to do with 
isolation of buds below the cooled zone is shown by the fact that a tempera- 
ture of 5°-6° C, applied to the upper end of an internode, produces at first 
marked retardation of growth of the tip but no growth of buds below, while 
the same temperature applied near the lower end of the internode produces 
no appreciable retardation of the tip, but the buds in the axil below develop. 
In general, the farther away from the axils to be isolated the low temperature 
is applied, the less effective it is in producing growth of the buds and vice 
versa. These facts suggest that the inhibiting factor, if it passes at all 
through a cooled zone, undergoes a gradual return or approach to its 
original effectiveness in its further course, so that when the cooled zone is 
2 In the original presentation of these and other experimental data lantern slides were 
used. 
