38 ARISAEMA TRIPHYLLUM 
There is not in any case a distinct bundle sheath, the vascular 
elements being surrounded by chlorophyll-bearing parenchyma. 
The presence of chlorophyll in the cells bordering the vascular 
elements is so. marked as to give a striking appearance to cross 
sections, which show all but the innermost bundles distinctly green. 
THE RAPHIDE CELLS 
From the first, A. triphyllum has been noted for its intensely 
acrid sap. This feature alone is sufficient to protect its green 
parts and the corm with its store of starch from the ravages of 
animals of all sizes. The North American Indians are reported 
by Havard (16, p. 106) to have found that by drying and cooking, 
the corms could be made edible. Sometimes in laboratories it is 
considered a lark to cook and eat Indian turnip corms. The 
writer has found them quite palatable when cut up and boiled for 
a half hour or more with one or two changes of water. 
The irritating principle is the raphides of calcium oxalate which 
are found abundantly through the plant, and which are always 
floating free in the sap exuding from wounds. Barnes (3) found 
that by filtering the expressed sap twice through filter paper, and 
so removing the needle-like crystals, it lost all its acridity. At- 
tempts by the writer to find any volatile oil or other irritating 
substance have given but negative results. 
The raphide-bearing cells are found almost throughout the 
plant. They have not been found in the mature embryo, in root 
caps, within limits of vascular strands or in epidermal structures. 
They are especially plentiful in leaf laminae, fruit, and corm. 
In the leaf the specialized cells occur in palisade or spongy 
tissue and are often close beside veinlets. Here they are for the 
most part long, more or less sinuous cells with fascicles of crystals 
extending in the general direction of the long axis of each cell 
(TEXT FIGs. 48-50). The size and shape of the cells may vary in 
one part of the plant, as shown in the figures just cited. Even 
wider variation is to be found in different parts of the plant. In 
the scape, spadix and petiole the cells are found chiefly near the 
periphery and are similar to those in the leaf. In the corm some 
cells ares lightly larger and more globular ‘than those containing 
starch, and they contain numerous small bundles of raphides 
