392 Prof. De Brignoli and Prof. Morren"o/i the 



above. In its ordinary state, the leaflets, all quite open, quite 

 flat, spreading out upon the same plane, nearly touch at 

 their margins, beginning from the reddish zone, which then 

 seems to form a continuous circle on a deeply divided leaf. But 

 if you have just given the petiole some gentle filKps, in a 

 quarter or half a minute, when the sun shines upon the plant, 

 you see the leaflets fold up along their midrib, from the base 

 to the apex, then the two lobes curve inwards, and lastly the 

 partial petiole bend from above downwards, so as to cause the 

 leaflets to hang down. Two or three minutes after the fillips 

 the plant seems to be asleep. 



A leaf teratologically developed with five leaflets exhibited 

 the same fact. It is unquestionably the species in which these 

 movements can be best observed. 



These were the only species which were at my command. 

 In all of them the movement takes place without a shock, 

 without agitation, but little by little, insensibly; it can, 

 however, be ascertained all the better, as between a leaf the 

 leaflets of which are horizontal, and another where they are 

 vertical, the difference at once strikes the eye. 



Our indigenous species are too small for observing the or- 

 gans of this mobility w ell, but Oxalis Deppei is well calculated 

 for observation and anatomy. 



As in all plants moveable from excitation, the organs of mo- 

 tion reside in the apparatus itself which moves. Now here 

 the apparatus consists of: 1. The blade itself of the leaf, an 

 organ of incurvation ; 2. The large midrib ; 3. The partial 

 petiole ; the former being an organ for folding back, the latter 

 an organ of incurvation. 



Now the blade of the leaf is composed, above, of a cuticle 

 with pinenchymatous cells, that is to say tabular-shaped (Mey- 

 en) ; beneath, of a cuticle with merenchymatous cells, swollen 

 up, like bladders, with numerous small linear stomata be- 

 tween all the raised cells, so that one amongst them is often 

 surrounded by six stomata ; in the middle by a double dia- 

 chyma, whose upper plane is formed of prismatic or ovoidal 

 cells placed perpendicularly, and of such a size that upon the 

 length of a single tabuliform cell of the upper cuticle [derme) 

 there are six utriculi of the diachyma. The plane of the dia- 



