INTRODUCTION 7 



of the germplasm and chromosomes, which are con- 

 cerned with the heredity of the plant and its trans- 

 mission. Around the cytoplasm is a membrane or 

 ectoplasm limited by the cell-wall, with which it is 

 confluent. 



Various vacuoles occur in the protoplasm formed 

 in the meshes of the network. These take part in 

 the isolation of useless material, or excretion, and in 

 nutrition. 



This network is filled with cell-sap, containing 

 water with nutrient salts in solution, food, etc. It is 

 the protoplasts to a great extent that build up the com- 

 pounds mentioned (post) from the nutrient salts that 

 are carried to them in water from the roots, and from 

 the carbon derived from the carbon dioxide of the air. 



The ectoplasm serves to retain the substances in 

 the water, but allows the water to be withdrawn by 

 osmosis. The strength of the solutes regulates the 

 latter. The ectoplasm also helps to build up the 

 cell-wall. 



The cytoplasm, in which the nucleus and plastids 

 are contained, is filled with cell-sap, and the starch, 

 proteids, etc., manufactured from the crude materials 

 it receives by absorption and photo-synthesis. The 

 cytoplasm assists, on division of the nucleus, in the 

 removal of the chromosomes to the opposite extremity 

 of the cell, preparatory to the formation of germ-cells. 

 It also takes part in the elaboration of the carbo- 

 hydrates, proteids, etc., and the formation of ferments 

 or enzymes which serve to digest the reserve materials 



