334 0N TIIE STEM 0F TnriES ' 



external ap- mercury, in which the quantity of new matter is hot more 

 pcarance. ^ aii i-oVff> or ^ iat Dctvveen tne metals and their suboxides, 



some of [which contain less than _~ of oxigen, will not be 

 disposed to question the principle, that minute differences 

 in chemical composition may produce great differences in 

 external and physical characters. 



(To be continued in our next.) 



II. 



On the Stem of Tfecs ; with an Attempt to discover the 

 Cause of Motion in Plants. By Mrs. Agnes Ibbetson. 



To Mr. NICHOLSON. 



SIR, 



Method ofdi- JL HE manner in which Linnaeus divided the stem of trceS 

 •f trees 16 StCm wasmaturally suggested by its appearance to the eye, little 

 aided by glasses : cortex, the rind ; liber, the bark ; lignum, 

 the wood ; and medulla, the pith. But at this time, that 

 our magnifiers are so perfected; nature points out a more 

 regular division, and one marked not only by the form, 

 but by the difference of the juices, with which the parts are 

 swelled. Indeed so different are the purposes to be effected, 

 and so clear are the divisions nature has made ; that, when 

 seen much magnified, they appear to me' directly to strike 

 the mind, and convince the reason ; provided the study is 

 pursued in a manner, that will enable the person, by a 

 view of the different parts properly prepared, to judge 

 sanely on the subject. The vegetable cuttings sold with the 

 solir microscope will do very well for superficial learners, 

 but no person can understand the nature of plants, or ex- 

 pect to profit from knowledge so obtained, who does not 

 cut his own specimens, and generally from fresh plants. 

 / It is laborious and troublesome, and requires great care ; 

 but I have never a moment repented the time so expended, 

 as from dried cuttings much of the real nature and all the 

 To judge from motion escape. Still both are to be consulted; and the 

 both dried and proper method is perhaps to compare them together. I 

 fresh cuttings. r * , \ x • * i_ u .1 u ■ 



copy from no book, every experiment has been made by 



myself, and carefully repeated a number of times : I may 



perhapt 



