76 < HLL CONTEXTS. 



Text Book, p. 110; Strasburger, p. 11; Goodale, p. 49; Bessey, p. 

 54; Bot. Centralbl., LV. (1893) p. 157. 



Illustration Second : Showing CRYSTALLOIDS. HYPODERMAL 

 TISSUE of POTATO TUBER. 



PREPARATION : Sections should be made below the cuticle, but 

 very near the surface, and the parenchyma should contain but a 

 few small starch grains. 



OBSERVE: 1. The rectangular cells with cell nuclei if present. 



2. Crystalloids, cubical in outline, surface plane, or some- 

 times eroded. 



3. Upon the application of iodine, observe yellowish tint 

 given to crystalloids indicating their nitrogenous nature. 



4. After drawing off a considerable portion of the fluid under 

 the cover-glass and subsequently applying a saturated solution of 

 common salt (NaCl), observe the changes in, and final dissolution 

 of, the crystalloids. True crystals are not thus acted upon. 

 Strasburger, p. 25; Goodale, p. 47; Vines' Text Book, p. Ill 



Illustration Third : ALEURONE AND STARCH. THE GARDEN 

 PEA (seed of Pisum sativum.) 



PREPARATION: Separate the cotyledons of the pea, and cut 

 away a portion of one with a knife. Then with the heel of the razor 

 make several small sections from the smooth surface. Mount in 

 glycerin. 



OBSERVE: 1. The grains of starch; their form and concen- 

 tric lines of structure or stratification. 



2. Their lines of fissure. 



3. The minutegrains in the cell with the starch, t\iealciiroc 

 grains. 



4. The cell structure and intercellular spaces. 



Draw, showing the above characters; then treat the section 

 with strong iodine and observe its effect on the aleur<m<-. 



Goodale, p. 47; Vines' Text Book of Bot., p. 112; Strasburger, 

 p. 18. 



Illustration Fourth : STARCH, ALEURONE, and the STRUCTURE 

 OF CEREAL GRAINS. Grain of WHEAT ( Triticntn />ul</<(re.) 



PREPARATION : By cross-section cut away one-third of the 

 grain. Make several thin sections from this surface, which sliull 

 include only a small portion of the coats of the grain, and of the 



