The Movements and Habits of Climbing PlantsDarwin, Charles
Science
The Movements and Habits of Climbing Plants
Darwin, Charles
Climbing plants; Geotropism; Plants; Plants -- Irritability and movements
COMMELYNACEÆ.—_Flagellaria Indica_.—From dried specimens it is manifest
that this plant climbs exactly like the _Gloriosa_. A young plant 12
inches in height, and bearing fifteen leaves, had not a single leaf as
yet produced into a hook or tendril-like filament; nor did the stem
revolve. Hence this plant acquires its climbing powers later in life
than does the _Gloriosa_ lily. According to Mohl (p. 41), _Uvularia_
(Melanthaceæ) also climbs like _Gloriosa_.
These three last-named genera are Monocotyledons; but there is one
Dicotyledon, namely _Nepenthes_, which is ranked by Mohl (p. 41) amongst
tendril-bearers; and I hear from Dr. Hooker that most of the species
climb well at Kew. This is effected by the stalk or midrib between the
leaf and the pitcher coiling round any support. The twisted part becomes
thicker; but I observed in Mr. Veitch’s hothouse that the stalk often
takes a turn when not in contact with any object, and that this twisted
part is likewise thickened. Two vigorous young plants of _N. lævis_ and
_N. distillatoria_, in my hothouse, whilst less than a foot in height,
showed no sensitiveness in their leaves, and had no power of climbing.
But when _N. lævis_ had grown to a height of 16 inches, there were signs
of these powers. The young leaves when first formed stand upright, but
soon become inclined; at this period they terminate in a stalk or
filament, with the pitcher at the extremity hardly at all developed. The
leaves now exhibited slight spontaneous movements; and when the terminal
filaments came into contact with a stick, they slowly bent round and
firmly seized it. But owing to the subsequent growth of the leaf, this
filament became after a time quite slack, though still remaining firmly
coiled round the stick. Hence it would appear that the chief use of the
coiling, at least whilst the plant is young, is to support the pitcher
with its load of secreted fluid.
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