164 STUDY or COMMON PLANTS. 



XVII. THE ARUM FAMILY. ARACE^. 



MATERIAL EEQUIRED. 



Entire plants of Indian tui-nip, Arisama triphyllum, Torr., in flower. 

 Similar specimens of skunk-cabbage, Symplocarpus foetidus, Salisb. 

 Flowers of cultivated calla, Richardia Africana, Kunth. 

 Other plants of this order that are procurable, such as sweet-flag, 

 Acorits Calamus, L., and any of the cultivated aroids. 



INDIAN TURNIP. Ariseema triphyllum, Torr. 

 General Characters. 



Examine entire specimens in a fresh condition. Note 



I. The thick, rounded, underground stem, corm, more or 

 less wrinkled externally. 



II. Long fibrous roots growing out from its upper part. 



III. Above ground, the smooth, cylindrical stem with 

 membranaceous, sheath-like leaves below, and one or two 

 large, compound, foliage leaves above. Describe the latter 

 in detail. 



IV. The peculiar venation, differing from that of a 

 majority of monocotyledons. Sketch one of the leaflets in 

 outline, and point out the mechanical advantages. 



V. Note the acrid taste due to the mechanical effect of 

 the raphides (crystals) on the tongue and throat. 



Inflorescence and Flowers. 



I. The inflorescence is covered by a peculiarly shaped, 

 arched spathe. Compare this in a number of specimens, 

 and note variations. 



