10G ME. DARWIN ON CLIMHING PLANTS. 



helix - ), Ficus repens, and F. bai-hatus, have no power of movement, 

 not even from the light to the dark. As previously stated, the 

 Hoya carnosa (Aselepiadacea?) is a spiral twiner, andean likewise 

 adhere by rootlets even to a flat wall ; the tendril-bearing Big- 

 nonia Twcedyana emits roots, which curve half round and adhere 

 to thin sticks. The Tecoma radieans (Bignoniacett), which is 

 closely allied to many spontaneously revolving species, climbs by 

 rootlets ; but its young shoots apparently move about rather more 1 

 than can be accounted for by the varying action of the. light. 



I have not closely observed many root-climbers, but can give 

 one curious little fact. Ficus- repens climbs up walls just like Ivy; 

 when the young rootlets were made to press lightly on slips of 

 glass, they emitted (and I observed fcnia several times), after about 

 a week's interval, minute drops of clear fluid, not in the least 

 milky like that exuded from a wound. This fluid was slightly vise-id, 

 but could not be drawn out into threads ; it bad the remarkable 

 property of not drying. One drop, about the size of half a pin's 

 head, I slightly spread out, and scattered on it some minute 

 grains of sand. The slip of glass WES left exposed in a drawer 

 during hot and dry weather, and, if the fluid had been water, it 

 would certainly have dried in one or two minutes ; but it remained 

 fluid, closely surrounding each grain of sand, during 128 days: 

 how much longer it would have remained I caunot say. Some 

 other rootlets were left in contact with the glass for about ten 

 days or a fortnight, and the drops of fluid secreted by them were 

 rather larger, aud so viscid that they could be drawn out into 

 threads. Some other rootlets were left in contact during twenty- 

 three days, and these wen' firmly cemented to the glass. llenee 

 we may conclude that the rootlets firsl secrete a slightly viscid 

 fluid, and that they subsequently absorb (for we have seen that it 

 will not dry by itself) the watery parts, and ultimately leave a 

 cement. When the rootlets were torn from the glass, atoms of 

 yellowish matter were left on it, which were partly dissolved 

 by a drop of bisulphide of carbon; and this extremely volatile 

 fluid was rendered, by what it; had dissolved, very much less 

 volatile. 



As the bisulphide of carbon has so strong a power of softening 

 indurated caoutchouc*, 1 soaked in it during a short time many 



* Mr. Spiller has recently shown (Chemical Society, Feb. 16, 18G">), in a 

 paper on the oxidation of india-rubber, thai this substance, when exposed to 

 the air in a fine state of division, gradually becomes converted into brittle, 

 resinous matter, very similar to shell-lac. 



