ACRIDITY OF TARO LEAVES. 69 
leaves, with deep basal sinus, and in its prickly stem. (PI. XLIX.) 
It is very distinct, however, in having about its base the mass of 
spines referred to. They are wiry and branching, and haye very 
much the appearance of sharp compound fishhooks. In reality they 
are lateral roots which differ from typical monocotyledonous roots in 
their hard woody structure and the absence of root caps. Mr. T. G. 
Hill and Mrs. W. G. Freeman, who made a study of the root structure 
of an allied species growing in Africa, found that ‘‘the lateral roots 
form the actual spines. They only exhibit normal root-structures at 
the extreme apex; elsewhere the phloem strands travel regularly 
throughout the whole area of the stele, while the xylem is more or less 
restricted to the central region. The hardness both of the main roots 
and the spines is due to the thickening and lignification of the con- 
junctive tissue of the stele.” Whether or not these spines have been 
specially developed for the purpose of protecting the edible tuber may 
be questioned, but that they do protect it is certain. 
Among the principal food staples of Guam is the taro, Caladium 
colocasia, & plant of the Arum family. Both the land and water varie- 
ties (Pl XXIV) are found invariably to have their smooth, succulent, 
satiny leaves free from the ravages of snails, insects, or herbivorous 
animals. Cattle and chickens delight in nipping off the young leaves 
of bananas and plantains; deer often inflict serious injury on a young 
coconut plantation in a single night; hreadfruit trees suffer from the 
attacks of all herbivorous animals, and must be protected from them— 
fruit, leaves, and bark; and even tobacco will be devoured in the field 
by insect Jarve unless it is ‘arefully watched and attended, On chew- 
ing a small portion of a taro leaf, the cause of its safety from attack is 
at once apparent. The tongue, roof of the mouth, and lining of the 
throat seem to be pierced by a thousand tiny needles, The allied 
Alocasiae, plants also belonging to the Araceae, alled **piga” by the 
natives of Guam, are so very acrid that the skin is sometimes stung 
by merely rubbing against one of their leaves. Not only is the root 
of the taro edible, but the tender young leaves are eaten like spinach 
or asparagus. When not thoroughly cooked, however, they retain 
their acridity, and in Polynesia it is a common occurrence to expe- 
rience an intense inflammation or burning of the throat after a meal of 
savory taro tops cooked with cocoanut custard, 
Through the courtesy of Dr. H. W. Wiley, Chief of the Bureau of 
Chemistry, United States Department of Agriculture, a careful chem- 
ical and histological examination of fresh taro plants was made for me 
by Mr. Lyman F. Kebler and Mr, B. J. Howard. The result of their 
examination and experiments tends to corroborate the theory that the 
burning sensation experienced on chewing the leaves is not caused by 
an acrid fluid, but by minute needle-like crystals of calcium oxalate 
« Annals of Botany, vol. 17, p. 415, 1905. 
