STRUCTURE OF PROTEID GRAINS 27 



the stained oil globules. Some larger droplets of oil may appear outside of 

 the section. Sketch, using h.p. if necessary. 



Repekences. Strasburger-Hillhouse, 6; Tschirch, 74. 



16. Structure of proteid grsiins (aleurone grains). A large part of the proteid 

 reserve material of seeds is stored in the form of minute bodies known as 

 aleurone grains. They occur in abundance packed around the starch grains 

 in such seeds as those of the bean and pea, but are more easily studied in 

 seeds nearly or quite free from starch. Kemove the testa from a seed of 

 the castor-oil plant {Ricinus) and cut thin sections from the endosperm. 

 Mount in olive oil (which does not dissolve any of the proteid material) and 

 examine with h.p. Note the very small aleurone grains, each with a clear body 

 at the narrow end. This clear body, called the globoid, is of mineral material, 

 principally a double phosphate of lime and magnesia. Draw the aleurone 

 grains. Mount another section in water and examine ; then run in absolute 

 alcohol under one edge of the cover glass, and note the proteid crystal, which 

 should appear plainly, constituting a large part of the bulk of the aleurone 

 grain, and the globoid. The latter is now distinctly recognizable as a solid 

 substance. Draw. 



Aleurone grains may be more easily demonstrated in thin sections of the 

 kernel of the Brazil nut. These should be rinsed twice in chloroform, to 

 remove the oil, then once in alcohol, and mounted in alcohol. Examine 

 with h.p., run in iodine solution while under the microscope, and note the 

 brown-stained grains in the cells. Draw. 



Refbkences. Strasburger-Hillhouse, 6 ; Tschirch, 74. 



MOVEMENTS, DEVELOPMENT, AND MORPHOLOGY 



OF THE SEEDLING 



EXPERIMENT XI 



Is the arch of the hypocotyl due to the pressure of the soil on the rising 

 cotyledons ? Sprout some squash seeds on wet paper under a bell glass, and 

 when the root is an inch or more long hang several of the seedlings, roots 

 down, in little stirrups made of soft twine, attached by a mixture of equal 

 parts of beeswax and rosin melted together to the inside of the upper part of 

 the bell glass. Put the bell glass on a large plate or sheet of glass on which 

 lies wet paper to keep the air moist. Note whether or not the seedlings form 

 hypocotyl arches, and, if so, whether the arch is more or less perfect than 

 that formed by seedlings growing in earth, sand, or sawdust. 



