J 58 ANATOMY A5TD PHYSIOLOGY OF THE VEGETABLE CELL. 



the stem the cellular tissue of the rind has already attained a considerable 

 longitudinal extension, compared with the parts situated nearer the axis. 

 Whether the movements which Dutrochet observed (" Ann. d Sc. nat 

 2 Sir.'' XX. 30 G) m the stems of Fi^um sativum, are identical with the 

 above-il escribed circular movements of twining planfe, with which, as I 

 shewed in the '' Botanische Zeitimg;' 1845, 118, Dutrochet was but very 

 imperfectly acquainted ; or whether, as appears to follow from his descrip- 

 tion, they depend upon a rotation of the stem miconnected with torsion, 

 I cannot decide, since I have not yet repeated these observations. 



Motion is also produced without external influence in tendrils, 

 which, in like manner, is capable, although in less degree than 

 the circular motion of twining plants, of bringing them in contact 

 with foreign bodies. For, when a tendril has attained its full 

 length, np to which time it is straight, it curls up together spirally 

 from its point to its hase, in such a way that its upper side fornn 

 the outer side of the spiral. When the tendril is brought in con- 

 tact with a foreign body by this movement, its irritability is 

 excited at the point of contact, and the above-described convolu- 

 tion round the support commences, which progresses from below 

 upwards along the tendril. 



These movements of tendrils and twining plants have not at- 

 tracted the attention of naturalists in so high a degree as the move- 

 ments of the leaves of Hedysarwrn gyrans. This plant possesses 

 ternate leaves ; the middle leaflet exhibits the ordinary sleep- 

 movements, sinking by night and rising by day, but the very 

 small side-leaflets present, day and night, a jerking motion, by 

 which they are alternately raised and depressed. Similar move- 

 ments are presented by the lateral leaflets of Hedysarum gyroides, 

 according to Mirbel, also of H. vespertilionis, and according to the 

 statements of JSTuttall ('' Genera of N. American Plants,'' ii. 110), 

 those of H. cuspidatum, and probably of H, Icevigatum. Few 

 plants have been so much observed on account of a physio- 

 logical peculiarity, as Hedysarum gyrans, but unfortunately all 

 attempts to give a tenable. explanation of its movements have 

 been fruitless. 



A similar motion, occurring without external cause, was dis- 

 covered by Lindley in the labellum of an Orchideous plant, Megan 

 cUnmrnfalcatuTYh, and more minutely observed by Morren (''Ann, 

 des Sc. nat. 2 Ser, xix. 91). This movement consists of a slow 

 depression and elevation of the labellum, repeated in periods of a 

 few minutes. From Morren's anatomical investigation, it appears 

 that this motion must be caused by an alternating expansion, 

 first of the upper, and then of the under, part of the cellular tissue, 

 which forms the claw of the labellum ; but the cause of these ex- 

 pansions remains just as obscure as that of the movements of the 

 leaves of Hedysarum gyrans. 



