36 ALEURONE GRAINS, CRYSTALLOIDS, GLOBOIDS. 
show that all the crystals hitherto found are composed of cal- 
cium carbonate, as those in the cystoliths, and in some of the 
lower Fungi ; or of calcium oxalate. The latter salt crystallises 
in two forms according to the proportion of water it contains. 
Thus in the one case when the crystals contain six equivalents 
of water of crystallisation, they form octahedra (fig. 55), as in 
the conglomerate raphides or sphzeraphides ; and, on the other 
hand, when there are only two equivalents of water of crystal- 
lisation, then bundles of acicular crystals or true raphides are 
produced (figs. 56 and 57). 
Fie. 57. Fie. 58. Fre. 59. 
Fig. 57. True or acicular ravhides of an Arum being discharged through 
endosmose under the influence of water.—Fig. 58. Cystolith, from 
Parietaria officinalis ——Fig. 59, Cystolith, from the leaf of Ficus elastica. 
After Henfrey. 
ALEURONE GRAINS, CRYSTALLOIDS, AND: GLOBoTDS.—Besides 
the inorganic crystals just described, it frequently happens that 
some of the protoplasmic matter in the cells, more generally in 
those of the albumen and cotyledons of ripe seeds—that is, in 
those cells in which reserve food material is stored up—assumes 
a crystalline form and becomes cubical, octahedral, tetrahedral, 
rhomboid, &c. (fig. 60). These are not however true crystals, 
as is seen by their angles not being very clearly defined by the 
action of various reagents, such as dilute caustic potash, which 
causes them to swell up and increase very much in volume, 
These crystalline masses are known as erystallcids or proteime 
crystals. They are readily seen when a transverse section of 
the albumen of the Castor-oil seed is placed in dilute glycerine 
and water (fig. 60). 
In the cells again of the albumen and cotyledons of ripe 
seeds we have, in addition to starch and oily matter, small 
roundish and colourless albuminous grains, which are termed 
proteid or alewrone grains (fig. 61, a, a). They are especially 
abundant in oily seeds, as in those of the Castor-oil plant, where 
they appear to replace starch ; but in those seeds where starch 
is abundant, these grains may be seen between the starch-grains, 
as in the Pea (fig. 61, a, a), Bean, Sweet Chestnut, and Grasses. 
In these grains the erystalloids just described are frequently 
found imbedded, and also peculiar small rounded bodies termed 
