THE MAGAZINE 



OF 



NATURAL HISTORY, 



FEBRUARY, 1837. 



ORIGINAL COMMUNICATIONS. 



Art. I. Remarks on a particular Form of Irritability observed in 

 the Stems of many Plants, especially Exogens, evinced on divid- 

 ing them in the Direction of their Axis. By Goldj no Bird, 

 F.L.S. F.G.S., Lecturer on Experimental Philosophy at Guy's 

 Hospital, &c. 



We are indebted to Dr. H. Johnson of Shrewsbury for 

 the first notice of the very curious and interesting fact of the 

 peculiar kind of vegetable irritability on which I am about to 

 offer a few remarks. This gentleman observed that, " on 

 dividing the stem of almost any herbaceous plant, a singular 

 separation of the divided segments uniformly occurs; and that 

 this separation continues until the stem withers and dies from 

 the loss of its moisture." This discovery was made known 

 by Dr. Johnson, in a memoir read before the Ashmolean 

 Society of Oxford, and subsequently published in the Philo- 

 sophical Magazine for March, 1835. 



If a portion of the stem of an herbaceous exogenous plant, 

 but especially those with fistulous stems, as any of the La- 

 biatae, be divided longitudinally, in the direction of the axis 

 of the plant, the division extending to the length of about 

 2 in., the divided portions will instantly separate from each 

 other to the distance of 1 in., or even more; this separation 

 constantly occurring, in whatever direction the plant may be 

 held. The same thing occurs if the young shoots of woody 

 stems are substituted for those more strictly herbaceous ; the 

 young branches of the common privet (Ligustrum vulgare), 

 as well as of the jasmine, and many others, possessing this 

 property of diverging on being divided, in a remarkable 

 manner. 



From a consideration of the facts thus briefly enumerated, 

 Dr. Johnson was induced to attribute the cause of this di- 



Vol. I, — No. 2. n. s. F 



