250 



CONTENTS AND PRODUCTS OF CELLS 



late crystals, as in grape seed. To study aleurone grains 

 and their inclusions: Cut a thin cross -section of the 

 peripheral cells of a grain of wheat and mount in alcohol. 

 Stain with an alcoholic solution of iodine to color the grains 

 yellow, and examine with the highest power. Make a 

 sketch of a few layers of cells, just beneath the epidermis. 

 Make a sketch of a few of the grains removed from the 

 cells. While looking at the mount run a little water under 

 the cover glass and watch the result. Make a similar 

 mount and study of the endosperm of castor -oil seed, or 

 of grape seed. In the castor- oil seed look for inclusions 

 of large crystaloids and small globoids. In the grape seed 

 globoids should be found with crystals of calcium oxalate 

 within them. This experiment will require the power of 



t- or 



inch objective. 



404. Cells may contain crystals. Besides the crys- 

 tals which are found as inclusions of aleurone grains, 

 many others may be found in many plants. In onion 

 skin they are prisms; in night -shade they 

 are in the form of crystal flour; in the 

 petioles of the peach they are roundish, with 

 many projecting angles ; in the rootstock of 

 skunk cabbage and the bulbs of hyacinth they 

 are needle-shaped and are called raphides 

 (Fig. 393). In the leaf of 

 the India-rubber plant (com- 

 mon in greenhouses) are found compound 

 clusters resembling bunches of grapes, 

 which are called cystoliths (Fig. 394). 

 These are concretions and not true crys- 

 tals. In saxifrage mineral matter appears 

 as incrustations on the surface of the 

 plant. Towards autumn, crystals of calcium oxalate be- 

 come very abundant in the leaves of many deciduous trees : 

 examine cross -sections of peach petiole in June and again 



393. Raphides of 

 rhizome of. skunk 

 cabbage. 



391. Cystolith in leaf 

 of rubber plant. 

 Ficus elastica. 



