ORGANS OF NrTEITIOK. 



63 



i^^;^. 153 



filled up by solid matter, to which the name of intercellular sub 

 stance has been given. 

 This appears to be of 

 the natiire of the 

 cuticle, and in some 

 instances, as we have 

 seen, it is in connexion 

 with that structure 

 through the orifices of 

 the stoma'ca, forming 

 with it the so-called 

 cistome. Formerly 

 this intercellular sub- 

 stance was supposed 

 to be universally dis- 

 tributed between the cells, glueing them together as it were, and 

 in some plants occurring in great abundance, as in many Algse, 

 the horny albumen of seeds, between the collenchymatous cells 

 of the common Beet, &c. In these cases the intercellular sub- 

 stance has now been proved to consist really of secondary 

 deposits inside the cells, as may be seen after the application 

 of iodine and dilute sulphuric acid to such tissues (figs. 153 

 and 154). 



Fig. 153. Section of the albumen of the seed of 



Betel-Nut Palm (^Areca Catechu). 

 Fig. 154. The same, after treatment with sulphuric 



acid and iodiue. After Henfrey. 



CHAPTEE 3. 



ORGANS OF NUTRITION OR VEGETATION. 



Having now fully considered the elementary structures of 

 plants, we proceed to describe in detail the various compound 

 organs which they form by their combination. These com- 

 pound organs, as already noticed (page 12), are arranged in two 

 divisions, namely: 1. Organs of Nutrition or Vegetation, and 

 2. Organs of Eeproduction. The root, stem, and leaves, form 

 the organs of nutrition ; and the flower and its parts the organs 

 of reproduction. Upon the whole, it is most convenient to com- 

 mence our notice of the oi'gans of nutrition with the stem, which 

 we now proceed accordingly to describe. 



Section 1. Tke Stem or Ascending Axis. 



The stem may be defined as that part of the axis which at its 

 first development in the embryo takes an opposite direction to the 

 root, (hence it is termed the ascending axis)"seeling the light 

 ^wntJ air, and bearing on its surface leaves and other leafy appen- 

 dages {fig. 15). This definition will, in numerous instances, only 

 strictly apply to a stem at its earliest development, for it frequently 



