PBOTOPLASM AND PLANT-CELLS. 



17 



grains) in the cells (Fig. 9). Apply iodine, wliich will stain the aleu- 

 roue yellow or brownish yellow. 



(6) Make a similar study of the aleurone of the bean. 



(c) Make sections of the foregoing and mount in water to observe 

 the solution of the aleurone-grains. The process may be hastened 

 by adding a very little potassic hydrate. 



(H) Make thin cross-sections of a wheat-kernel and study the glu- 

 ten (aieurone) cells of the inner bran. Add iodine. 



(e) Make a similar study of the bran of rye, oats, and Indian corn. 



26. Crystals. — Some cells of certain plants contain crys- 

 tals (Pig. 12). These are of 

 Tarious shapes, one of the 

 most common forms being 

 needle-shaped, while others 

 are cubical, prismatic, etc. 

 They are frequently clus- 

 tered into little masses. 



27. Crystals are for the 

 most part composed of cal- 

 cium oxalate. That is 

 are a combination of 

 and oxalic acid. 



they Fig. 12.— Crystals of calcium oxa- 

 late. The right-hand portion of 

 hme the figure shows two cells of Rhu- 

 barb, with their contained crystals, 

 A fpTV Tinvp and one enlarged. On the left Is a 

 ^j.ew iid.VB cry gtal from the beet. Much magnl- 



a different chemical compo- *'^'^' 



sition — as the calcium carbonate crystals found in nettles, 

 hops, hemp, etc., besides others of still less frequent oc- 

 currence. 



28. Crystals appear to be the residues from chemical re- 

 actions which take place in the interior of plants, and they 

 probably have no further use. 



Practical Studies. — {a) Mount in water several thin longitudinal 

 sections of the stem of the Spiderwort (Tradescantia) and note the 

 bundles of needle-shaped crystals in enlarged, thin-walled cells. 

 Many crystals will be found floating free in the water, having been 

 separated in the preparation of the specimen. 



(J) Similar sections of the stem of the Evening Primrose, Fuchsia, 



