I46 PART II. VEGETABLE HISTOLOGY. 



Treat a small quantity of Potato or Corn starch with saliva, keeping the 

 mixture at the temperature of about 90° F. for a few hours, and then examine. 

 Only the transparent skeletons of the former grains will be left, and if these be 

 treated with iodine, no blue coloration will be developed. The granulose has 

 been dissolved, leaving only the starch cellulose. 



5. For the study of inulin, make some moderately thin sections of the 

 roots of the Dahlia, Dandelion or Chicory that have been gathered in the 

 autumn ; soak them for a few hours in strong alcohol, and then examine them. 

 Sphere crystals of inulin, which may be distinguished from starch and mineral 

 crystals by the fact that they stain a yellowish color with iodine, will be found 

 in some of the cells. 



6. For the study of aleurone grains and crystalloids, make some thin sec- 

 tions of the flesh of the seed of the Castor Oil plant or of the Brazil nut ; soak 

 the sections for twenty-four hours in alcoholic solution of corrosive sublimate, 

 so as to render the pioteids insoluble ; stain them in solution of eosin ; then 

 place them on a glass slip in solution of potassium acetate, and examine them. 

 Some of the aleurone grains will be observed to be amorphous, and others will 

 be seen to contain crystalloids and globoids. Draw some of the different 

 forms. 



Treat a fresh section of the same seed with concentrated solution of potas- 

 sium hydrate, and then afterward dilute the solution with water by running a 

 little under the edge of the cover-glass, and then immediately observe. A 

 slight swelling of the crystalloid will be observed when the potassium hydrate 

 is added, but when water is added it swells rapidly and dissolves. All the 

 other proteids are similarly affected, but mineral crystals, if present, remain 

 unchanged. Aleurone grains may also be studied by laying the freshly cut 

 sections in a drop of water and immediately examining. The water does not 

 at once disintegrate the aleurone grain, owing to the oil present. If now a 

 drop of absolute alcohol be run under the cover glass, the crystalloid within the 

 aleurone grain will come distinctly into view. 



Fine cubical crystalloids may also be found in the outer portion of the 

 potato tuber.' 



7. For the study of plant crystals, thin sections of the stems, leaves or 

 roots of the following plants may be made : 



Raphides are abundant in the Evening Primrose, the Calla Lily, the Indian- 

 turnip and most other members of the Arum family, as well as in many liliaceous 

 plants. 



Sphere-crystals are abundant in medicinal Rhubarb, in the Yellow Dock 

 and in the Hollyhock and most other Malvaceous plants. 



Other forms may be found in the stems of the Cactuses, in the stems and 

 leaves of the Begonias, in the leaves of the Century Plant, etc. 



Crystoliths of great beauty are obtained by making thin cross sections of 

 the leaves of the common Nettle and of Ficus elastica. They are also found in 

 the leavesof many other members of the Urticacea?, and also in some Acanthacea:. 



Plant crystals may be studied to advantage by means of polarized light, and 

 a magnifying power of from 200 to 500 diameters should be used. 



