AMERICAN 
JOURNAL OF BOTANY 
Vol. V November, 191 8 No. 9 
CALCIUM OXALATE IN THE DASHEEN* 
O. F. Black 
Calcium oxalate enters into the composition of a great variety of 
plants. As it is a quite insoluble salt, when synthesized by the plant 
it separates as a solid from the plant juices. It is probably formed 
during protein metabolism and is considered by most authorities as a 
waste product of such action, although a few plant physiologists 
maintain that it is dissolved and utilized in the further growth of the 
plant. However, the solid crystals may easily be detected under the 
microscope in various forms in plant tissues. Not infrequently they 
are found in bundles of fine, needle-like crystals packed in cells and 
surrounded by a mucilaginous liquid. Crystals of this character are 
called "raphides," and the cells containing them when brought in con- 
tact with water have the property of ejecting the individual needles 
which float out slowly into the surrounding medium. Plants which 
produce calcium oxalate in this form, when eaten raw, invariably cause 
a painful burning sensation in the mouth, the obvious explanation of 
which is that when the cells full of needles meet the saliva of the mouth 
the needles are ejected and penetrate the mucous membrane, although 
other explanations are conceivable. 
Among the plants which synthesize calcium oxalate in this interest- 
ing form is the dasheen (Colocasia esculenta (L.) Schott.), which has 
been introduced into this country by the Office of Seed and Plant 
Introduction of the United States Department of Agriculture, and 
has been successfully grown in Florida, where it has shown every 
promise of becoming a valuable addition to our vegetable food supply. 
The tubers of this plant can be utilized as a substitute for potatoes, 
while the large leaves when boiled have proved excellent greens. There 
* Published by permission of the Secretary of Agriculture. 
[The Journal for October (5: 397-446) was issued Nov, 9, 1918.] 
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