CHAP. I. 



CELLULAR TISSUE. 



riddled full of holes (/y.2.), the aperture of which 

 does not exceed the -J,o of a millimetre (or of 

 half a line) ; or are less frequently pierced with 

 transverse slits, which are occasionally ^ 

 so numerous as to transform the bladders 

 into a real articulated tissue, as in the 

 pith of the Nelumbium {fi(j. 3.)." This 

 ,j^„^ statement is now well known to have 



been founded upon inaccurate observation ; what the 

 supposed pores really are has already been explained. (See 



^ With reference to this subject, it maybe also observed, that 

 the bladders often contain air-bubbles, which appear to have 

 no direct means of escape, and that the limits of colour 

 are often very accurately defined in petals, as, for mstance, in 

 the stripes of tulips and carnations, which could not be the 

 case if cellular tissue were perforated by such holes as have 

 been described; for in that case colours would necessarily run 



together. , . i t 



One of the most striking instances with which I am ac- 

 quainted, of ceUidar tissue having the appearance of pores, is 

 in Calycanthus, where it was pointed out to me by Mr. Ya- 

 renne. (Plate I. fig. 1.) But even in this, a carefid ex- 

 amination ^^-ith glasses of different magnifying powers shows 

 that the apparent pores are certainly not such, but composed ot 

 a solid substance, which may be distinctly seen by varying the 

 direction of the rays of the transmitted light with which it 

 is viewed. Sometimes they appear like luminous points ; by 

 a little alteration of light they acquire a browmsh tint; and it 

 seen with the highest powers of a compound microscope, where 

 there is a great loss of light, they become perfectly opaque. 



Cellular tissue is always transparent and colourless, or at 

 most only slightly tinged\vith green. The brilliant colours 

 of vecretable matter, the white, blue, yellow, scarlet, and other 

 hues "of the corolla, and the green of the bark and leaves is 

 not owang to any difference in the colour of the bladders, but 

 to colouiing matter of different kinds which they contam. 

 In the stem of the Garden Balsam (Impatiens balsamma), a 

 single cell is frequently red in the midst of others that are 



B 4 



