46 MB. DARWIN ON CLIMBING PLANTS. 



and the hook remained ODen for thirty -three 



during 



very 



As soon as 



'lin 



a ring, its sensibility, both within and without, is lost ; but as 

 long as the hook remains open its sensibility is retained. 



When the plant had grown from the bulb to the height of only 

 about six inches, the leaves, four or five in number, were broader 

 than those subsequently produced, and their soft and but little- 

 attenuated tips did not form hooks, and were not sensitive ; nor 

 did the stem revolve. At this early period of growth, the plant 

 can support itself; its climbing apparatus is not required, and 



therefore is not acquired. 



rown plant 



which was flowering, and which would not have grown any taller, 

 had leaves on the summit, which were not sensitive, and could not 

 clasp a stick. 



Flagellaria Indica (Commelynacese). — -From dried specimens 

 it is manifest that this plant climbs exactly like Gloriosa. A 

 young plant, 12 inches in height, and bearing fifteen leaves, had 

 not one leaf as yet produced into a hook or tendril-like filament ; 

 nor did the stem revolve. Hence this plant acquires its climbing 

 power later in life than the Gloriosa lily. According to Mohl 

 (S. 41), TTvularia (Melanthaceae) climbs like Gloriosa. 



These three last-named genera are all Monocotyledons ; but 

 there is one Dicotyledon, namely Ne^pentlics^ which is ranked by 

 Mohl (S. 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 twisting round 

 any support. The twisted part becomes thicker; but I observed 



Mr 



any 



thickened. 



N. l<evis and N. 



latm^ia^ in my hothouse, whilst less than a foot in height, showed 

 no sensitiveness in their leaves or power of movement or of climb- 

 ing. But when N. Icsvis had grown to a height of 16 in 



first 



there were signs of these powers. Each young leaf when 

 formed stands upright, but soon becomes inclined ; at this period 



growt 



than 



any other part. The 



came 



round and firmly seized it. But 



