PROTOPLASM AND PLANT-CELLS. 



11 



which are concentrically striated. Now add a small drop of iodine 

 and note the blue coloration, which becomes purple or purple-black 

 if much iodine is used. 



(6) Make an extremely thin slice of the potato-tuber and treat as 

 before, so as to observe starch grains in 

 the cells. By staining such a section 

 with carmine the protoplasm in the 

 starch-bearing cell may be made evi- 

 dent. 



(c) Study the starch of wheat, rice, 

 Indian corn, oats, etc. 



(d) Mount carefully a few threads of 

 Pond Scum (Spirogyra) which has been 

 for some hours in the sunlight. Note 

 the aggregations of minute starch-grains 

 in the spiral chlorophyll-body (Fig. 6). 

 Now add iodine and observe the color- 

 ation of starch-grains. 



(e) Make thin sections of leaves which 

 have been in the light for some hours, 

 and observe minute starch-grains in 

 the chlorophyll-bodies. Use iodine as 

 above 



(/) Make longitudinal sections of 

 ripened apple-twigs and note the starch 

 stored in certain cells of the pith for use 

 when growth is resumed. 



24. Aleurone. — In mature seeds 

 and tubers there are commonly to 

 be found small rounded granules 



of albuminous matter to which the Scum'(s'pirogyra^. showing-sptral 

 « 4 . , T . chlorophyll-bodies, each with ag- 



name oi Aleurone has been given gregations of starch. At a and b 



. . T . . - the cells are beginning to branch 



(Fig. 6). It is, in part at least, preparatory to uniting. Magni- 



the protein matter of the older 



botanists. It is also identical with what has been called 



the gluten of the grains of wheat, rye, oats, etc. 



25. Aleurone is poorly understood, but it appears to be 

 a dry resting state of protoplasm. Some, if not all, of it 



