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199, 205.
[page 70]
growing part continues to do so, probably for as long as growth continues.
This movement of the radicle has been described in Brassica, Aesculus,
Phaseolus, Vicia, Cucurbita, Quercus and Zea. The probability of its
occurrence was inferred by Sachs,* from radicles placed vertically upwards
being acted on by geotropism (which we likewise found to be the case), for
if they had remained absolutely perpendicular, the attraction of gravity
could not have caused them to bend to any one side. Circumnutation was
observed in the above specified cases, either by means of extremely fine
filaments of glass affixed to the radicles in the manner previously
described, or by their being allowed to grow downwards over inclined smoked
glass-plates, on which they left their tracks. In the latter cases the
serpentine course (see Figs. 19, 21, 27, 41) showed unequivocally that the
apex had continually moved from side to side. This lateral movement was
small in extent, being in the case of Phaseolus at most about 1 mm. from a
medial line to both sides.


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