THE PLANT-OMLL. 



17 



examples of large cells are found in the Thallophytes ; Nitella, 

 for example, has cells 50 mm. (3 inches) long, and 1 mm. 

 (.04 inch) thick. According to Von Mohl, the bast-cells 

 of a species of palm {Astrocaryum) are from 3.6 to 5.6 mm. 

 (.13 to .21 inch) in length. For ordinary plants the average 

 size of the cells may be given as from .1 to .02 mm. (.004 to 

 .0008 inch). From this average size the dimensions of cells 

 decrease to exceedingly small magnitudes. In the Yeast 

 Plant {Saccharomyces cerevisim) the cells are about .008 mm. 

 (.0003 inch) in diameter. The cells of Bacterium lermo are 

 from .0021 to .0028 mm. long and from .0028 to .0005 mm. 

 broad (.0001-.00008 by .00008-.00002 inch). 



The following table, taken from Hofmeister's " Lelire von der Pflan- 

 zenzelle," ia useful as showing how the dimensions of similar cells 

 vary in different plants : 



Table of Dimensions of Vahiotts Kinds of Cells op Woody 

 Plants. 



(In decimals of a millimetre.) 



t^ o S 



S] n u 





Cambium-cells, average length 



Vessel-like wood-cells, average lengtli.. 



Bast-like wood-cells, average length 



Vessel-cells of the wood, average length 



Latticed cells of young secondary bai-K, aver- 

 age length 



Bast-cells of young secondary bark, average 

 length 



Cells of medullary ray in the cambium ring, 

 maximum length in tangential pection 



Do,, do., maximum widtu in tangential sec- 

 tion 



Cells of medullary ray in the young wood, 

 average length in tangential section 



Do., do., average width in tangential section. 



Cells of medullary ray in the young secon- 

 dary hark, average length in tangential 

 section 



Do., do., average width in tangential sec- 

 tion 



339 

 1.179 



.615 



.403 



.017 



.567 

 .037 



.504 

 .076 



.786 



I'sio 



1.158 



.630 

 .075 



.744 

 .076 



1,511 

 2 020 



2.183 



.049 



.014 



.095 

 .019 



