MTNUTK ANATOMY OF FLoWiailNd J>LANTS ^If) 



parent nucleus are assured to the two resulting nuclei. 

 Onl}' after the nucleus of a cell has hnished its division, 

 is the surrounding cytoplasm separated into two portions. 

 The production of two cells from one is completed by the 

 formation of a new transverse wall. 



498. Many cells possess, in addition to the nucleus, pro- 

 toplasmic organs perforuiing special oftices in the genei'al 

 work of the cell. Cells from tlie interior of the leaf, for 

 example P^ig. 382, contain numerous rounded or lens- 

 shaped bodies, lying in the cytoplasm near the walls. 

 These bodies, colored green l>y tlie chlorophyll pigment 

 which tliey t^ontain, are the 

 cJiIorophi/Il grdiiides or clilo- 

 rojilastlilH. Tliey.give plants 

 their characteristic green 

 color. They are active in 

 carbon assimilation. Simi- 

 lar cell organs, with red 

 or yellow pigment instead 

 of green, give color to 

 fruits and flowers. Tlie\' 

 are called chroinoplastiilH. 



A tliin external layer of 

 the cydoplasm next tlie cell 

 wall may be distinguished 

 by its superior clearness and 

 the absence of granulation. 

 It is very probable that this 

 really constitutes a sort of 

 membrane, possessing a closeness of structure and tenacity 

 above that of the rest of the cytoplasui. The remainder 

 of the cytoplasm is highly granular in appearance, owing 

 chiefly to the varying density of the protoplasm itself. 

 Except in their earliest stages active cells contain inter- 

 spaces, or vacuoles, filled with water and dissolved sub- 

 stances (Fig. ot)2). One large vacuole may fill the 

 greater part of the cell, tlie protoplasm forming a layer 

 next the wall. The watery contents of the vacuole or 



