THE GENERAL STKUCTUEE OF PLANTS 



certain cells of Tradescantia and Chelidonium, a similar 

 streaming of the protoplasm is observable (fig. 8). Such 



FIG. 7. CELLS FBOM THE LEAF 

 OF Elodea. x 300. 



, nucleus ; p, protoplasm, in which 

 are embedded numerous chloro- 

 piasts. The arrows show the 

 direction of the movement of the 

 protoplasm. 



>'*/ 



FIG. 8. Two CELLS FKOM A 

 STAMINAL HAIB OF Trades- 

 cantia. x 800. 



The arrows show the direction 

 of the movement of the 

 protoplasm. 



movements are spoken of as rotation when the current 

 flows uniformly round the cell, or as circulation when the 

 path has a more complicated course. 

 It has been mentioned that, 

 with very rare exceptions, all cells 

 contain a specially differentiated 

 portion of protoplasm, known as the 

 nucleus (figs. 6 and 9). This struc- 

 ture does not occupy a very definite 

 position in the cell, but not infre- 

 quently is found almost in 

 centre. If the whole of the space is 

 not filled with protoplasm, the part 

 in which the nucleus lies is con- 

 nected with the lining layer by means of strands or 

 bridles. In other cases the nucleus is embedded in 



4-Vvp FIG. 9. NUCLEUS OF A CELL, 

 SHOWING ABBANGEMENT OF 

 THE CHBOMATIN THBEADS. 

 x 1000. 



a, threads ; b, nucleolus. 



