20 



tint. These leiicoplastids, of which a great many are 

 often found in each cell, have been derived from the 

 typical rhodoplastid of the assimilating- cells. 



The Leiicoplastids of the conducting cells and the faintly 

 coloured rhodoplastids of the coHecting cells are both very 

 active in depositing starch. Starch is never noticed in the 

 assimilating celts. 



The starch grains take the form of flattened discs. 

 They stain brownish when treated with iodine. The 

 florideau starch is slightly different in its reaction after 

 treatment with iodine from the starch of the potato, the 

 grains of which stain blu'^ with iodine. 



4. — Histolog*y of the Root. 



The histology of the root calls for no special remarks. 

 The cell walls do not swell up nuich with fresh water. 

 The pits also are not of the same large form met with in 

 the shoot. 



The cells of the root are found to be quite full of starch, 

 which by its presence almost completely obscures the 

 rhodoplastids. The root organ is clearh' red, but the red 

 plastids are hardly visible. They are apparently finely 

 divided, consisting of darker red masses, which are con- 

 nected with one another by faintly coloured strands. 



C. — Physiology of the Vegetative Organs. 



TJnder the heading of Physiology, reference may be 

 made to the functions of the three tissues of the shoot. It 

 is, as already mentioned, to their supposed physiological 

 function that they owe their names. 



The Assimilating Cells are obviously correctly named. 

 Assimilation is conducted by means of the rhodoplastids. 

 The fixation of carbon dioxide and the subsequent elabora- 

 tion of complex organic from simple inorganic compounds 



