188 BOTANICAL GAZETTE [MARCH 
is most marked within 1™ of them, and the older part is straight. 
This difference could not occur if each zone were not able both 
to be geotropically irritated, and to respond to the irritation. If 
the experiments lasted several days it was found that the stems 
which were fixed at the apex were usually more curved than 
those fixed normally, at the base, so that in this case the end in 
the air was carried well beyond the vertical position. This was 
obviously because the youngest part remained horizontal, and as 
the older part matured with more or less curve the part still 
growing kept bending itself upright, and so carried the older 
part beyond the vertical. 
The hypocotyls of Helianthus annuus and Lupinus albus and 
the epicotyls of Piswm sativum and Phaseolus vulgaris were tested, 
but showed no behavior different from that of Cucurbita, so that 
it is not worth while to encumber this paper with the individual 
results. The nutation of Phaseolus caused some queer curves, 
and the same would probably be found the case with Cucurbita 
when the epicotyl changes from orthotropic to plagiotropic. 
The behavior in response to stimulation by light is analogous. 
No experiments were undertaken especially to show this ; but 
when seeds of Lupinus were germinated in holes in a floating 
cork ina glass vessel, and grew so that the cotyledons kept their 
place while the hypocotyls extended downward into the water, 
the latter became concave on the light side, and the roots were 
carried toward the window. 
Any indication of real polarity is likewise wanting in roots. 
This is not easily demonstrated, as the curvature is largely exe 
cuted in the roots of the plants I have been using, within Loa 
of the tip, and it is difficult to imbed them so that the tip will 
stay fast without encasing the part which should be free to react. 
Nevertheless, I have succeeded occasionally with the roots of 
Cucurbita, Lupinus, Helianthus, and Pisum, and in every cas€ 
the result was an excess of growth of the upper side of the root, 
by which the shoot end of the plant was carried downward. 
This went as far as about 90°, but I have hitherto been unable 
to make the tip stay imbedded while the free end is bent 
