[BOOK i. 



BOOK I. 



ORGANOGRAPHY ; OR, OF THE STRUCTURE OF PLANTS. 



CHAPTER I. 



OF THE ELEMENTARY ORGANS. 



IF plants are considered with reference to their internal 

 organisation, they appear at first sight to consist of a vast mul- 

 titude of exceedingly minute cavities, separated by a mem- 

 branous substance ; more exactly examined, it is found that 

 these cavities have a variety of different figures, and that 

 each is closed up from those that surround it ; if the inquiry 

 is carried still farther, it will be discovered that the partitions 

 between the cavities are all double, and that by maceration 

 in water, or by other methods, the cavities with their enclosing 

 membrane may be separated from each other into distinct 

 bodies. These bodies constitute what is called Vegetable 

 Tissue, or Elementary Organs : they are the Similary parts 

 of Grew. 



The organic basis of the elementary organs is called 

 cellulose, a ternary compound, derived from cambium or 

 organic mucus, a viscid azotised quaternary secretion, which 

 occurs everywhere in young parts, and as a residuum in 

 old parts. This organic mucus, or cambium, is also named, 

 by Vegetable Physiologists, organisable matter. 



Organic mucus has long been known as a substance exist- 

 ing in Algals, prior to the appearance of organisation, as in 

 Protococcus nivalis, &c. It has been found by Brongniart, 

 Henslow, &c. in the form of cuticle, a thin homogeneous 



