THE VEGETABLE CELL 303 



such a piece of tissue and mounted in water will show large 

 sphsero-crystals of iniilin, often extending through several con- 

 tiguous cells (Jig. 660). 



The amides, such as asparagiu, leucin, &c., which are found 

 in the cell-sap, are generally the result of the decomposition of 

 proteid material. They are very prominent in young seedlings 

 and in germinating seedg. 



In many cells the peculiar bodies spoken of as enzymes 

 occur. These are ^-ery varied, and a discussion of their pecu- 

 liarities must be deferred to a later section of this work. They 

 can only be detected in cells by the results of their activity. 



The cells vary much in size in different plants, and in 



Fig. 660. 



Fig. 660. SpliEero-crystals of inuliii from the Articlioke. A. Small irystiils in 

 interior of cells. B. Large crystals extending through many cells. ( x 250.) 



different parts of the same plant. Polygonal or oblong cells, on 

 an average, vary from about ^ J^ to yj^j^j of an inch in diameter ; 

 others again are not more than ^^jy ; while in some cases they 

 are so large as to be visible to the naked eye, being as much as 

 ^ or even ^ of an inch in diameter. The largest occur in the 

 pith of plants, in succulent parts, and in water-plants. 



The dimensions of elongated cells generally afford a striking 

 contrast to those of polygonal ones ; for while we find that their 

 transverse diameter is commonly much less, averaging about jjj\(^ 

 of an inch, and frequently not more than ^ij"Biri they become 

 much more extended longitudinally, sometimes reaching four, 

 five, or more inches in length. More generally, however, they 

 vary from about :^ io ^ oi an inch in length. 



