38 MB. DARWIN o.N (IJMIHXli PLANTS. 



" dwarf crimson Nasturtium " had no power of revolving ; but they 

 moved during the day to the light, and from it at night, in a 

 rather irregular course. The petioles, when well rubbed, showed 

 no power of curving ; nor could I see that they ever clasped any 

 neighbouring support. AVe have seen in this genus a gradation 

 from species such as T. tricolorum, which have exquisitely sensi- 

 tive petioles, and intcrnodes which have rapid revolving powers 

 and can spirally twine up a support, to other species, such as 

 T. eleaans and T. tuberosum, the petioles of which arc much loss 

 sensitive, and the intcrnodes of which have very feeble revolving 

 powers and cannot spirally twine round a support, to this last 

 species, which has entirely lost or never acquired these faculties. 

 From the general character of the gemis, the loss of power seems 

 the more probable alternative. 



In this species and in T. elegans, and probably in others, the 

 flower-peduncles, as soon as the seed-capsule begins to swell, 

 spontaneously bend abruptly downwards and become somewhat 

 convoluted : when a stick lies in the path, it is to a certain extent 

 clasped ; but, as far as I have been able to observe, the movement 

 of the peduncle is quite independent of the stimulus from contact. 



Antireiiineje. — In this tribe (Lindlcy) of the Scrophulariacea?, 

 at least four of the seven included genera have leaf-climbing 

 species. 



Maurandia JBarcIai/ana. — A thin, slightly bowed shoot made two 

 revolutions, following the sun, each in 3 h. 17m. ; this same shoot, 

 the day before, revolved in an opposite direction. The shoots do 

 not spirally twine, but climb excellently by the aid of the young 

 sensitive petioles. These petioles, when lightly rubbed, move after 

 a considerable interval of time, and subsequently become straight 

 again ; a loop of thread weighing ^th of a grain caused them to 

 bend. 



Maurandia semperflorens. — This freely growing species climbs 

 exactly like the last, by its sensitive petioles. A young internode 

 made two circles, each in lh. 46 m. ; so that it moves almost twice 

 as rapidly as the last species. But I should not have noticed the 

 present species, had it not been for the following unique case. 

 Mohl says (S. 45) that "the flower-peduncles, as well as the 

 petioles, are wound into tendrils ;" and he adds nothing more 

 about the genus. But it must be observed that Mohl classes as 

 tendrils even such objects as the spiral flower-stalks of the Vallis- 

 neria. Nevertheless this remark, and the well-known fact that 

 the flower-peduncles of this Maurandia are ilexuous, led me care- 



