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TEXTBOOK OF BOTANY 



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Fig. 31. Photomicrograph of a vertical section of a stem tip of coleus. The small 

 meristematic cells at the extreme tip are completely filled with protoplasm. The 

 older cells which have become much enlarged by vacuolation are similar in 

 structure to those in Fig. 30. Photo by E. B. Wittlake. 



take place in them, often resulting in the accumulation of particular 

 substances, such as starch and chlorophyll. There are usually several to 

 many plastids in each cell; and as the cells multiply by division, the 

 plastids also increase in number by division. They are named on the 

 basis of certain substances that accumulate in them, as shown in 

 Table 1. 



In very young cells there are small colorless plastids ( leucoplasts ) 

 that apparently may develop into these more specialized types, depend- 

 ing upon environmental conditions. 



The nucleus. The nucleus is usually more refractive to light than the 

 cytoplasm and under the microscope appears brighter. Often its proto- 



