CELLULAR STRUCTURE 



95 



If we examine the cells of other plants, we find that these chrom- 

 atophores vary greatly in size and shape. The other parts of 

 the cell are not so easily recognized. But if we will keep some of 

 the algae in alcohol for a few hours the chlorophyll will be partly 

 or entirely removed so that we can recognize the very delicate 

 layer of protoplasm lying next to the cell- 

 wall and also delicate strands extending 

 across the cell. This will be greatly 

 aided by treating the algse with eosin or 

 some other coloring matter which will 

 stain the protoplasm. In this plant, the 

 protoplasm does not completely fill the 

 cell, but there are large spaces which are 

 filled with water or air and known as 

 vacuoles. We will also be able to recog- 

 nize the nucleus which is a very import- 

 ant part of the cell. 



The nucleus is protoplasmic in char- 

 acter and very complicated in structure. 

 It is present in nearly all living cells, and 

 when the cell divides the nucleus also divides, one part going 

 into each new cell. In a few plants, the cells are multinuclear, 

 and when they divide some nuclei are found in each new cell. 



Cells also contain many compounds. The most prominent 

 is the atarch, which can be readily recognized by examining 

 a very thin section of potato or apple under the microscope. 

 If we treat this section with iodine, the starch grain will turn 

 blue. The starch grains of different plants differ in size and 

 form; this fact enables the microscopist to decide on amount 

 and character of many adulterations of foods and drugs. The 

 cells also contain sugar, fats, oils and other compounds which 

 will be discussed later. (Chapter IX.) 



As the plant grows the cells undergo many changes and modi- 

 fications. These variations are much more pronounced in the 



FIG. 69. A typical plant 

 cell showing protoplasm. 



