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in his work on “The Movements of Plants.” He says that while 
apheliotropism may act in some slight measure, geotropism is un- 
questionably the exciting cause of the downward movement. He 
gives as proof of this the fact that gynophores grew straight down 
when the light in the greenhouses entered from one side as well as 
from above. His conclusions were corroborated by the experiments 
with the gynophore hairs already described, as they served at the 
same time to exhibit the geotropism of the downward movement. 
The light came to these plants through one window at the side. 
When the tips of the gynophores were pointing downward, the 
position of the stems was so changed as to reverse the direction 
of the tips, causing them to point directly upward. In a very 
short time a curve was formed in the growing portion of the gyno- 
phore, just below the apex, bringing the tip again to its former 
position, that is pointing directly downward. There were also 
some slight indications of a tendency of these organs to curve 
away from the light. 
Darwin also refers to the means by which the organ is enabled 
to force its tip into the ground and make its way through it. The 
sharp, smooth point of the gynophore, he says, would probably 
enable it to penetrate the ground by mere force of growth, but 
its action is aided by a circumnutating movement. In evidence 
of this, he gives the result of a number of observations where 
circumnutation plainly took place. 
By the study of its anatomy several other interesting facts 
have been obtained. First, the arrangement of the vascular tis- 
sues is such as to point clearly to its adaptation to the movement of 
the organ. The bundles, as before stated, run singly throughout 
its whole length. Furthermore, they lie close together and are 
characterized by heavy bast strands. The bast serves to strengthen 
the gynophore while pushing its way into the soil; at the same 
time pliability is given by means of the separate bundles which 
allow a freedom of motion not possible when there is a continuous 
ring. 
Another and much stronger feature is unquestionably that of 
the hairs which form near the tip of this organ whenever and 
wherever it reaches the ground and has projected its tip into it 
fora slight distance. By this means the part of the organ already 
