MISCELLANEOUS INTELLIGENCE. 237 



On tiir Sensitive plant.— The movement of the leaves of the Mimosa 

 Pudica have their origin in certain enlargements, situated at the articulation 

 of the leafets with the petiole, and of the petiole with the stem. Those only 

 which are situated in the last articulation are of sufficient size to be sub- 

 mitted to experiment. If, by a longitudinal section, the lower half of this 

 swelliug be removed, the petiole will remain depressed, having lost the 

 power of elevating itself: — if the superior half be removed, the petiole will 

 remain constantly elevated, having lost the power of depressing itselt. These 

 facts prove that the motions of the petiole dep nd on the alternate tur- 

 gescence of the upper and lower hall of the enlargment, situated at the 

 point of articulation: and that contractibility is not the principle of these 

 motions. 



If one part of the plant be irritated, the others will soon sympathise, or bear 

 witness, by the successive falling of their leaves, that they have successively 

 felt the irritation. — thus, if a leaflet be burnt slightly by a lens, the interior 

 movement which is produced will be propagated successively to the other 

 leaflets of the leaf, and thence to' the other leaves on the same stalk. A very 

 clever French experimentalist, Mons. Dutrochet, found. 



1st — That this interior movement is transmitted equally well, either as- 

 cending or descending. 



2nd — That it is equally well transmitted, even though a ring of bark has 

 been removed. 



3rd — That it is transmissible, even though the bark and pith be removed 

 so that nothing remain to communicate between the two parts of the skin: 

 except the woody fibres and vessels. 



4th — That it is transmissible, even when the two parts communicate merely 

 by a shred of bark. 



5th — That it may be transmitted, even when the communication exists by 

 the pith only. 



6th— But that it is not transmissible, when the communication exists merely 

 by the cortical parenchyma. 



From these very interesting experiments, it results that the interior move- 

 ment produced by irritation, is propagated by the ligneous fibres and the 

 vessels. 



The propagation is more rapid in the petioles than in the body of the stem: 

 — in the former it moves through a distance of from three to six tenths of an 

 inch in a second ; in the latter, through from eight to twelve hundredths of 

 an inch, during the same portion of time. External temperature does not 

 appear to exert any influence on the rapidity of the movement, but very 

 sensibly effects its extent. / 



Absence from light, during a certain time, completely destroys the irri- 

 tability of the plant. Such change takes place more rapidly when the tem- 

 perature is elevated, than when it is low. The return of the sun's influence 

 readily restores the plant to its irritable state. It appears, therefore, that it 

 is by the action of light, that the vital properties of vegetables are sup- 

 ported, as it is by the action of oxygen that those of animals are preserved, 

 consequently, etiolation is to the former what asphyxia is to the latter. 



Gardener's Gazette. C. Mackenzie. 



The causes of the variety and vividness of colours in flowers — 

 The petals of floweis do not owe their beauty to the colour that paints 

 them ; for that, when drawn off, is dull and dead ; neither do they owe 

 their brilliant tints to the skin that covers them. Their lovely appearance 

 is derived chiefly from the bubbles of water which compose their pabulum. 

 Receiving the sun's rays, they are enlivened and brightened by reflet tion 

 and refraction from those drops ofwater ; and from that spot or point of 

 light being seen in every bubble, and striking to the focus underneath. 

 By these means the whole flower would at times be one blaze of light had 

 not nature to soften the same, covered the petal with an upper and an 

 under ^in uhirh curtails their diamond-like rays, and leaves them, iu 

 Mmd. a lightness and beauty unequalled by the most exquisite art ol the 

 paiirti i 



