MINUTE ANATOMY OF FLOWERING PLANTS 217 



wheat, which is, or sliouhl be, a highly nutritious element 

 of wheat tlour. In the cells of the potato tuber are to be 

 found examples of proteid matter formed 

 into cubical cr^-stals. These granules and 

 crystals are storage forms of protein. 



501. Crystals of calcium compounds — 

 calcic carbonate and oxalate — are of very 

 common occurrejice (l'"ig. 305). These are 

 generally considered to be waste products 

 of the chemical changes going on in the 

 cells. 1 Other substances also occur in 

 crystalline form, but less frequently. 



502. The account here given (jf the typi- 

 cal vegetable cell, as regards protoplasmic 

 structures and cell contents, is of course 

 brief and incomplete; it is meant to be soo. Cells contain- 

 suggestive of tlie extent of the subject. "}S ueeiiU'- 

 The nature of the cell has been, and will (raphides)of 

 long continue to be, the obiect of the cak-mm oxa- 



. „ ■' late, 



investigations of numerous workers. 



503. Certain cells of certain plants regularly contain 

 more than one nucleus each. And in not a few of the 

 lower cryptogams great numbei's of nuclei exist within 

 a common wall. The many-brancliecl plant body may 

 in such cases consist of one continuous chamber witliout 

 internal division walls. Each nucleus represents a single 

 cell, but there is no corresponding division of the cyto- 

 plasm. 



504. The cell wall. — Early investigators assigned to 

 tlie cell wall the chief importance; but we now know that 

 life resides in the protoplasm, and that the wall is of 

 secondary importance. In many of the lower plants the 

 contents of certain reproductive cells break from their 

 walls, and s\vim freely forth (Fig. 285). Onl}' after ti 



matters in afldition to the carbon, hydrogen, and oxygen which compose 

 starch and sugar. Proteid substances enter directly, and as such, into 

 the composition of pirotoplasni. 



1 It is quite possible that calcium oxakxte is a storage form of food. 



