FORMS OF CELLS. 37 
globoids (fig. 60), which are composed of double phosphate of 
calcium and magnesium. 
The aleurone grains and crystalloids are evidently reservoirs 
of protein, to be used when growth becomes active in the process 
of germination, in the same way as starch and oily matters are 
reservoirs of hydrocarbons for use in a like manner. Aleurone 
grains are insoluble in alcohol, ether, benzole, or chloroform, 
but soluble in water. They are coloured brown by iodine, and 
other re-agents show that they are of an ‘albuminoid nature. 
The experiments of Weyl and Sidney Vines indicate that the 
proteids exist in these grains as globulins, which hitherto have 
been known only to occur in animals, that is, as myosin-globulin 
and vitellin-globulin. Vines has also found in the aleurone 
grains of the Pony a large quantity of hemialbumose, a sub- 
stance allied to the peptones. 
Fic. 60. Fie. 61. 
Fig. 60. Cell from the endosperm or albumen of the seed of the Castor-oil 
plant ( Ricinus communis) in dilute glycerine, showing large transparent 
proteid or aleurone grains, with crysta loids and globoids imbedded in 
them, After Sachs.—/Fig. 61, Cells of a very thin section through a 
. cotyledon of the embryo in a ripe seed cf the common Pea (Pisum 
sativum). a,a.Aleurone grains, st. Starch granules. i, i. Intercellular 
spaces. After Sachs. 
IJ. Forms anp Sizes or Crxis.—Having now described 
the nature of cells and their contents, we proceed to give a de- 
tailed account of the various forms and sizes which they are 
found to assume in different plants, and in various parts of the 
same plant. 
1. Forms of Cells.—Cells are of various forms ; thus, in the 
first place, as we have already partially seen on page 24, when 
the growth is uniform, or nearly so, on all parts of the cell-wall, 
we have a spherical or rounded cell (fig. 62); but when it is 
greater at the two extremities than at the sides, the form is 
oval or oblong (fig. 63). In the above cases, also, the cells are 
