Cusap. IL. TROPAOLUM. 61 
as thin as fine twine. One such shoot revolved in a 
course opposed to the sun, at an average rate, judging 
from three revolutions, of 1 hr. 23 m.; but no doubt 
the direction of the revolving movement is variable. 
When the plants have grown tall and are branched, 
all the many lateral shoots revolve. The stem, whilst 
young, twines regularly round a thin vertical stick, 
and in one case I counted eight spiral turns in the 
same direction; but when grown older, the stem often 
runs straight up for a space, and, being arrested by 
the clasping petioles, makes one or two spires in a 
reversed direction. Until the plant grows to a height 
of two or three feet, requiring about a month from the 
time when the first shoot appears above ground, no 
true leaves are produced, but, in their place, filaments 
coloured like the stem. The extremities of these 
filaments are pointed, a little flattened, and furrowed 
on the upper surface. They never become developed 
into leaves. As the plant grows in height new fila- 
ments are produced with slightly enlarged tips; then 
others, bearing on each side of the enlarged medial tip 
a rudimentary segment of a leaf; soon other segments 
appear, and at last a perfect leaf is formed, with seven 
deep segments. So that on the same plant we may see 
every step, from tendril-like clasping filaments to perfect 
leaves with clasping petioles. After the plant has grown 
to a considerable height, and is secured to its support 
by the petioles of the true leaves, the clasping fila- 
ments on the lower part of the stem wither and drop 
off; so that they perform only a temporary service. 
