BRIEFER ARTICLES. 
THE PROBABLE FUNCTION OF CALCIUM OXALATE 
CRYSTALS IN PLANTS. 
A RATHER comprehensive study of vegetable histology (medicinal 
plants), extending over a period of six years, has brought to my attention 
more specifically the great abundance and wide distribution of crystals 
of calcium oxalate, and has led to the formulation of a theory as to 
their probable function in the plant economy. 
There seems to be no logically deducible reason for assuming that 
the crystals serve as a protection against herbivorous animals, though 
such a theory was promulgated by Stahl and others and is now widely 
accepted by teachers of botany. 
Calcium oxalate occurs in four predominating form types. Of these 
the least common is the crystal sand (Krystallsand, Krystallmehl, 
Krystallpulver) which occurs in the roots of belladonna, in the stem 
parenchyma of Solanum dulcamara, species of Atropa, Datura, Physalis; 
bark of Sambucus, Cinchona, and in some other plants. The prismatic 
and aggregate forms are perhaps about equally common and are very 
widely distributed. The needle-shaped or acicular crystals are also 
very common, but predominate in monocotyledonous plants. 
Leaving out of consideration the still undecided question of the 
chemical formation of the crystals in the plant and the causes which 
lead to the production of one or the other form type, we shall refer 
briefly to their probable function. 
G. Kraus in 1891 expressed it as his opinion that calcium oxalate 
was a reserve product to be redissolved by the plant and again utilized. 
This applies, however, only to a part of the crystals deposited during 
the previous season. Calcium oxalate dissolves with difficulty. It is 
insoluble in water, alcohol, ether, acetic acid, saliva, and other animal 
secretions. Being insoluble in these substances it is also tasteless ; hence 
taste cannot enter as a factor to guard against destruction by herbivorous 
animals. Nor is this substance poisonous. Some of it would no doubt 
be decomposed by the secretions of the digestive tract (as free hydro- 
chloric acid in the stomach), but not enough to produce poisoning due to 
142 [auGusT 
i 
' 
i 
