CHAP. I.] 



PLANT ARCHITECTURE. 



33 



work. The cells in the central part of the stem of 

 some of our common rushes {Jwncus) have a stellate 

 form ; from a cell originally spherical several ray-like 

 prolongations are formed due to local growth of certain 

 portions of the cell- wall ; the tips of these rays are 

 joined to similar arms from adjoining cells, the whole 



Fig. 8. A single cell of the celandine 

 (Chelidonium majus) showing the cell- 

 wall lined inside by an irregular layer 

 of protoplasm from which strands, p, 

 pass into the large central sap-cavity ; 

 k, the nucleus, with a nucleolus. The 

 arrows indicate the direction of circu- 

 lation of the strands of protoplasm. 

 (Highly magnified. ) 



forming a light and porous tissue. The original very 

 thin wall is almost invariably thickened and strengthened 

 by the deposition of cellulose on its inner surface, but 

 this thickening matter is not uniformly deposited over 

 the entire surface, certain portions of the original thin, 

 cell-wall remaining unthickened. The cells are said to 



