228 
hardens, and increases in length, whilst the undeveloped leaflets 
may fall off, those of the opposite side, where the pulvinus 
is unattached, remaining and developing normally but occa- 
sionally falling off also. If the support is thin, the pulvinus 
makes 2 to 4 or so tight coils around it, if thick (0.8 to 
1 cm. diam.) not more than | coil. The “tendril” can, though 
thick, bend sharply round a corner and can apply itself closely 
to a four-cornered stick. The attached pulvinus becomes hard 
and woody, the unattached remains soft and flexible. 
| Pulvinus attached to support. After 1 week. Pulvinus of opposite leaf. No contact] 
Support. | N° of coils. | Diameter. | Length. | Length. | Diameter. 
‘ 100 mm. | | 100 mm 
2. mm. diam. S 230 3 em. || 2.3 em 195 «# After 
4 on ” 11/5 230 w | 33 n 18 » | D7O << 20 1 
Yi ” 1/5 aw 88 oe 214 | 145 week 
” ” 12/5 145 w | 88 -p 0.9 » | 160 »# 
1 em. by !/, em. 1 o> 6 ow 135 # 194 71 150» After 
RE oe l 945 » 133 4 || 2.2 9 | 145 w» {10 days. 
A comparison of transverse sections of attached tendrils with 
opposite unattached ones, shews that the most marked change 
takes place in the wood cylinder, which after 1 week’s contact 
may be from 4 to 6 times the thickness of that of the opposite 
unattached pulvinus. The outer layer of sclerenchyma is some- 
what thickened, but only owing to a thickening of the walls 
of its component cells and not to any increase in their numbers. 
The cortex as a whole is of the same thickness, being compo- 
sed of 20 or so layers of cells, but the cells are slightly larget 
and the walls thicker than in the unattached pulvinus. Whether 
the pulvini are with or without attached leaflets, the same 
differences exist, but are not quite so marked, when the leaflets 
are attached, as when they have fallen off. In the former case 
the attached pulvinus has a double function as an attaching 
organ and as a nutritive channel, the unattached functioning 
as a motile organ Supporting the leaflets and acting a5 ® 
nutritive channel as well, whilst in the latter case the atta 
ched pulvinus functions as a clasping organ only and the unat- 
tached is functionless, ; 
