CELL SAP 17 
and scattered throughout the specimen. These crystals are 
composed of calcium oxalate. Add a little hydrochloric acid 
and they will dissolve without effervescence. 
(k) Similar crystals may be found in many other plants, 
e.g. Indian turnip (Arisaema), evening primrose (Oenothera), 
fuchsia, garden balsam (Impatiens), garden rhubarb, ete. 
(1) For crystals of other types examine sections of prickly 
pear (Opuntia), young basswood twigs, scales of onion, stem of 
lamb’s quarters (Chenopodium), petiole of beet, etc. These 
are also composed of calcium oxalate. 
(m) Examine a thin cross-section of the leaf of the rubber 
plant (Ficus elastica). In some of the modified epidermal 
cells will be found peculiar stalked crystalline bodies of calcium 
carbonate deposited upon a cellulose core which hangs down 
into the cell cavity from the outer portion of the cell wall. 
Treat the section with hydrochloric acid. The cystolith, as it 
is called, dissolves with the evolution of COs, leaving the cellu- 
lose core, thus distinguishing it from calcium oxalate, which 
dissolves without effervescence. 
28. Cell Sap. The cytoplasm of a cell usually contains 
a large amount of water imbibed by it but not really a 
part of it. Water is also found fre- 
quently in drops (vacuoles) within 
the cell. This is the cell sap. It 
holds in solution the various soluble 
substances absorbed by the plant as 
well as those manufactured by the 
cell itself. It makes up by far the 
greater part of the bulk of the contents 
of the average cell. Among the sub- frye, 6.—Large vacuoles. 
stances dissolved in the cell sap, in 
addition to the mineral matters absorbed by the plant 
from the soil water, are many sorts of organic compounds 
produced by the cytoplasm. The most important of 
these are the various sugars and organic acids. The 
commonest of the sugars are saccharose or cane sugar 
2 
