26 CELLULAR TISSUE. [BOOK i. 



Padus), &c. An analogous phenomenon is also found in the 

 epidermis of the pericarp of Helleborus foetidus. 



But although the origin of the different forms of tissue 

 may be shown to be identical, it is obviously important to 

 distinguish them for practical purposes, in order to avoid 

 confusion, just as the organs of the flower, notwithstanding 

 their common origin, are regarded as if they were essentially 

 distinct. " If" as Link justly says, " we were to call the 

 external parts of the flower of grasses, bracts, or leaves, 

 because they, in point of fact, happen to be bracts, and 

 eventually leaves, it would give rise to infinite confusion ; 

 and how many terms would not be necessary in order dis- 

 tinctly to express what bract or what leaf is alluded to? 

 Raspail to be sure has adopted this singular manner of 

 describing grasses, and no confusion has followed ; but this 

 is because nobody has given himself the trouble to introduce 

 M. RaspaiPs treatise to notice." I shall therefore proceed 

 henceforward to speak of them as if they were distinct in 

 their origin. 



SECT. I. Of Cellular Tissue, or Parenchym. 



CELLULAR, UTRICULAR, or VESICULAR TISSUE, generally 

 consists of little bladders or vesicles of various figures, ad- 

 hering together in masses. It is transparent, and in most 

 cases colourless : when it appears otherwise, its colour is 

 usually caused by matter contained within it. 



If a thin slice of the pith of elder, or of any other plant, 

 be examined with a microscope, it will be found to have a 

 sort of honeycomb appearance, as if there were a number of 



