excitability and movement of the Leaves q/'Oxalis. 391 



lower surface around the common petiole which forms the 

 axis. This last movement is similar to that which takes place 

 in the evening at the time of the sleep of the plant^ and which 

 has caused these leaves to be called dependent {folia depen- 

 dentid) . 



Of our three indigenous species^ striata and corniculata 

 showed me these movements with the highest degree of energy, 

 Oxalis acetosella has them less strong, but perhaps may have 

 them as evidently when in flower, a time at which I have not 

 observed it. 



Every kind of exciting action provokes the same changes, 

 as the wind, and especially a slight compression of the mid- 

 dle of the leaf, or of the place where the three partial petioles 

 meet, between the thumb and fore finger. 



In the botanic garden of the University of Liege I also 

 observed two species with three folioles : Oxalis purpu- 

 rea (W.), and Oxalis carnosa (MoL). The first, when placed 

 in a hothouse, showed the phaenomena of excitability in the 

 highest degree. The three folioles, without considerably bend- 

 ing back their lobes by the movement of incurvation already 

 mentioned, curved downw ards so as to touch one another two 

 and two by the half of their limb, by placing their inferior sur- 

 face one against the other. 



Oxalis carnosa is more sluggish. The old leaves were mo- 

 tionless ; the young ones, especially those which clothe the 

 upper part of the stalk, exhibit nevertheless the same excita- 

 bility, but the movement of incurvation is also less evident 

 in it. 



In a sixth trifoliate species, Oxalis tortuosa, the leaflets 

 were no longer entire enough to enable me to ascertain if it 

 were equally excitable. 



Oxalis Deppei^, furnished with four leaflets, evinces an ex- 

 citability much more decided than the other species mentioned 



* The Oxalis Deppei brought from Mexico to England in 1827, and 

 figured by Mr. Loddiges in his 'Botanical Cabinet,' No. 1500, is the same 

 species as that which has been described and figured by our learned col- 

 league M. Lejeune in the Bulletin of the Academy, vol. ii. p. 334, 1835, by 

 the name of Oxalis zonata. Known throughout England by its older name, 

 I have thought it right to continue it. It is not from the Cape of Good Hope, 

 but from Mexico. 



