As we had observed that grease was highly injurious to some plants, we
determined to try its effects on radicles. When the cotyledons of Phalaris
and Avena were covered with grease along one side, the growth of this side
was quite stopped or greatly checked, and as the opposite side continued to
grow, the cotyledons thus treated became bowed towards the greased side.
This same matter quickly killed the delicate hypocotyls and young leaves of
certain plants. The grease which we employed was made by mixing lamp-black
and olive oil to such a consistence that it could be laid on in a thick
layer. The tips of five radicles of the bean were coated with it for a
length of 3 mm., and to our surprise this part increased in length in 23 h.
to 7.1 mm.; the thick layer of grease being curiously drawn out. It thus
could not have checked much, if at all, the growth of the terminal part of
the radicle. With respect to geotropism, the tips of seven horizontally
extended radicles were coated for a length of 2 mm., and after 24 h. no
clear difference could be perceived between their downward curvature and
that of an equal number of control specimens.
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