356 ELEMENTARY ORGANS. CHAP. III. 



tologists, and can only set down my own want of 

 success in discovery to the score of some defect, 

 either in the specimens examined, or in my mode 

 of examination. Indeed the only root in which 

 I have ever found them, after examining a very 

 considerable number, is that of the common garden 

 Lettuce, known by the name of Cos Lettuce. 

 Having taken the root of a plant that was just 

 putting out its flowers, and stripped it of its bark, I 

 then cut it partly across about the middle of its 

 length, and broke the remainder of it gently 

 asunder. On examining the surface of the frac- 

 ture with the microscope, fragments of spiral tubes 

 were seen projecting from it near the centre. 

 They did not seem very tenacious of their spiral 

 form ; and when once uncoiled did not readily 

 resume it. 



Or stem of The spiral threads are to be found also in the 

 plants^ stem and branch ; but not in all parts of them ; 

 or at least not in all periods of their growth. It 

 seems very doubtful whether they exist at all in 

 the bark. Daubenton professes indeed to have 

 seen them in it ; but I believe no one else ever 

 has ; so that we are perhaps sufficiently well war- 

 ranted in entertaining our doubts. It seems also 

 very doubtful whether they exist in that part of 

 the stem which consists of matured wood, though 

 Daubenton professes to have seen them in the wood 

 of the Cedrela; in "which case he does not alto- 

 gether stand alone; as they are represented both 



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