THE CELLULAR CONSTRUCTION OF THE PLANT 23 



FIG. 13. 



Optical longitudinal section of a single cell from the middle of a hair of the 

 Cucumber. Externally is the cell-wall. Its inner surface is lined by a layer of cyto- 

 plasm surrounding a large vacuole. In this the nucleus is suspended centrally by 

 numerous cytoplasmic threads. Movements may be seen in these during vitality 

 which convey granules, plastids and even crystals, thus showing active circulation 

 within the living cell. (After Sachs.) 



