ACRIDITY OF TARO LEAVES, 69 



leaves, with deep basal sinus, and in its prickl}^ stem. (PI. XLIX.) 

 It is very distinct, however, in having about its base the mass of 

 spines referred to. They are why and })ranehing-, and have very 

 much the appearance of sharp compound tishhooks. In reality the}^ 

 are lateral roots which differ from typical monocotvledonous roots in 

 their hard woody structure and the absence of root caps. Mr. T. G. 

 Hill and ]SIrs. 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 regularl}^ 

 throuo-hout the whole area of the stele, while the xvlem 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 lignitication of the con- 

 junctive tissue of the stele."'* Whether or not these spines have been 

 specialh^ 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 

 eo/ocasn(, a plant of the Arum familj'. Both the land and water varie- 

 ties (Fl. 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; breadfruit 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 tield 

 b}'^ insect larva? unless it is carefully 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 tin}^ needles. The allied 

 Alocasiae, plants also belonging to the Araceae, called "piga" ))y the 

 natives of Guam, are so ver}- acrid that the skin is sometimes stung 

 b}^ mereh' rubljing against one of their leaves. Not only is the root 

 of the taro edible, but the tender 3"oung leaves are eaten like spinach 

 or asparagus. When not thoroughly cooked, however, the^- 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 w^ith cocoanut custard. 



Through the courtesy of Dr. H. W, Wilev, 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 i\lr, 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 l)y 

 an acrid fluid, ])ut by minute needle-like crystals of calcium oxalate 



"Annals of Botany, vol. 17, p. 413, 1903. 



