CHAPTER I.— THE CELL. I45 



destroyed. It will be observed, also, that the chlorophyll-bodies have been 

 stained a brown color similar to, but owing to their density, a deeper brown 

 than that of the protoplasm. 



Soak a portion of a fresh leaf for twenty-four hours in strong alcohol, and 

 then observe the effects. The protoplasm has been killed, and has shrunken 

 so that the primordial utricle is no longer in contact with the cell-wall. Now 

 put this, together with a small portion of the fresh leaf, in borax-carmine solu- 

 tion for a few hours, and then observe the results. The nucleus and protoplasm 

 of that portion treated with alcohol will be found stained, while the living pro- 

 toplasm has not taken the staining material. This illustrates an important 

 difference between living and dead protoplasm. 



Protoplasmic movements similar to those seen in Vallisneria may be studied 

 in the young stinging hairs of the Nettle, in the blue, moniliform hairs borne 

 on the filaments of the Virginia Spiderwort, and in the leaves and large inter- 

 nodal cells of Chara and Nitella. 



For different forms of chlorophyll-bodies, study the leaves of any common 

 moss, thin sections of the leaves of Begonia, and filaments of Zygnema and 

 Spirogyra. The latter are common pond-scums, popularly known as brook- 

 silks, Figs. 372 and 373. Make drawings illustrating each study. 



3. Young cells for study may be found near the growing apex of stems 

 and roots. Thin sections of the tip of the radicle of the germinating Bean or 

 Pea, or of the sub apical portion of a young root of the Indian Corn, afford good 

 examples. Study the sections first in a drop of pure water ; then afterward 

 stain them with iodine ; examine and make drawings of them. If the thin 

 cell- walls cannot be distinctly seen by this treatment, clear one of the sections 

 by soaking it for a while in five per cent, solution of potassium hydrate, and 

 then afterward treating it with strong acetic acid, and finally examining it in 

 the solution of potassium acetate thus produced. 



4. For the study of starch grains, soften the fruits of any of the cereals, as 

 Indian Corn, Rice, Wheat, Oats or Barley, and seeds of the Leguminosae, as 

 Peas and Beans, in warm water ; make thin sections of them, and examine 

 them with a power of from 150 to 500 diameters. Examine, also, thin sections 

 of the Potato tuber and the fleshy rhizomes of Canna and Ginger in the same 

 way. 



Observe the position of the nucleus and the character of the markings. 



Treat the grains with a dilute solution of potassium hydrate by putting a 

 drop of the solution at one edge of the cover-glass and drawing it under by 

 means of a bit of blotting paper placed at the opposite edge, and immediately 

 examine. Observe that they swell, and at first the markings are rendered more 

 distinct, but afterward, by the imbibition of more water, they disappear, and 

 finally the grains themselves pass into solution. 



Stain another set of sections with dilute iodine solution, and observe that 

 the starch grains assume a violet-blue color. They may thus readily be dis- 

 tinguished from other cell-contents. 



Make careful drawings and measurements of the grains of several different 

 kinds of starches. 

 11 



