THE LIVING WORLD 211 



starch, sugar and other products. The ascending fluids 

 permeate from cell to cell upwards, while the products 

 of carbon-fixation permeate from cell to cell inwards. 

 Slow oxidation, or oxygenation (respiration), meantime 

 takes place in the ultimate component cells of the plant, 

 the respired air (containing much carbonic acid) mean- 

 while diffusing itself and escaping. During daylight the 

 balance of discharge is largely in favour of the oxygen, 

 but at night the balance of discharge is in favour of the 

 carbonic acid. 



Thus the plant lives and grows by the exercise of the 



FIG. 38. 



A LEAF OF BRYOPHYLLUM. 



Showing two young plants springing from its margin. 

 (After Geddes.) 



functions of absorption, circulation, feeding (or alimen- 

 tation) by its cells, together with respiration and se- 

 cretion. 



Generation, by the aid of the two sexual products (i) 

 the pollen tube, and (2) the embryo cell, provides for the 

 preservation of the race; but this is also abundantly 

 provided for in plants by another process by a sexless 

 (asexual) process of generation. In many plants aggre- 

 gations of cells form buds, called bulbils, which become 

 detached and then grow into a new individual plant. 



