242 BOTANICAL GAZETTE [APRIL 
In darkness 
Pot 17. One shoot (from a cut potato), 130™™ high, with large leaves. 
Pot 18. Two shoots (from a cut potato), 105 and 150™™ high, with large leaves. 
Although the plants were kept under these conditions for ten days, no intu- 
mescences were formed. The leaves on the plants in the dark became yellow 
and the plants finally died. 
EXPERIMENT VI 
Four pots of plants were placed in a shaded portion of the green- 
house over warm water pipes, where their roots would be kept warm. 
Pot 19. Two shoots (from a whole potato), 177 and 187™™ high, with large 
leaves. 
Pot 20. Two shoots (from a whole potato), 150 and 170™™ high, with large 
leaves. 
Pot 21. One shoot (from a cut potato), 85™™ high, with rather small leaves. 
Pot 22. One shoot (from a cut potato), 105™™ high, with rather small leaves. 
Resulis 
In four days the leaves of nos. 19 and 20 were nearly covered with intumes- 
cences. Pots 21 and 22 also produced them, but they were not as numerous as 
on the preceding, and the growth of the plants was more rapid. 
From this set of experiments it appears that intumescences appear 
in light and in the shade when the plants are abundantly supplied 
with water and their transpiration is reduced. They are found still 
more abundantly when their roots are kept warmer. Intumescences 
are not formed in complete darkness nor in light or darkness when 
the absorption of the roots is lessened by cold. Intumescences were 
not produced in any case on plants which were not covered by the 
bell jars. 
At the end of this series of experiments all the plants used, as well 
as those grown outside the bell jars, were cut down and allowed to 
grow up again. Healthy shoots came up from all the plants except- 
ing those which had been kept in darkness and had been killed by 
the rotting of their leaves and stems. In about ten days a few of the 
plants had reached a sufficient height to cover with the Leng jars and 
the preceding experiments were repeated. 
EXPERIMENT VII 
Plants placed in sunlight and covered May 7. 
Pot 23. Two shoots (from a cut potato), 140 and 120™™ high, with large leaves 
