ANATOMY OF THE CELL. 35 
magnesium, phosphoric acid, and a little organic matter. They 
are widely distributed, occurring in nearly all aleurone grains. 
The real crystals consist of calcium oxalate; they are of less 
Ve 
Lh) 
\ cs b 
S 
Fie. 18. 
Fic. 17. - aa : : 
f Aleurone grains from Ricinus, @ in thick 
A club-shaped hair of an etiolated potato stem glycerine, b in thin, showing the 
with erystalloids, *. #6 aleurone grains 1-5 enclosed erystalloids. The roundish 
from Ricinus seed; 8-9 from Momordica bodies are globoids. c¢ grain contain- 
seed. wv globoids. kk crystalloids. A x 300. ing crystal of calcium oxalate. 
B x 400. — (Aced, to Vogl.) (Th. Hartig.) 
frequent occurrence than the globoids, and are usually either 
needle-shaped or prismatic. 
In some instances the entire proteid matter of the aleurone 
grain takes the form of a crystal and is then known as a protein 
erystal instead of a protein grain. Between these protein crys- 
tals and the grains with several enclosed structures, various 
intermediate or transition forms occur. 
veserve material is also stored in various places in the plant 
in a different form from the two organized structures, starch and 
aleurone grains. For example, the carbohydrates are sometimes 
stored as cellulose, the nitrogenous substances, as amorphous 
proteids. All of these substances are non-diffusible and must 
undergo some change when it becomes necessary to convey them 
from one cell to another. The non-nitrogenous substances are 
changed to sugars, the nitrogenous to amides. 
This brings us to the consideration of the remaining sub- 
stances found in plant cells, many of which are organic but not 
