III.] 



PISTIACEJE. 



309 



cooking. It is a variable plant, as are most largely culti- 

 vated species, and some of its varieties have been separated 

 as distinct species. The aromatic Aconis Calamus^ with 

 sword-shaped leaves, common in Indian gardens, is a very 

 widely dispersed member of the Family ; occurring in Eng- 

 land, through Europe and temperate Asia, and also in North 

 America. The fragrant rhizome is chewed, made up as a 

 confection, or used medicinally. 



The leaves of Colocasia and some of its allies, growing 

 in swampy places, distil water from a minute pore at the 

 tip, to which point free canals, in the substance of the leaf, 

 converge. This process supplements the transpiration from 

 the surface of the leaf, and is most abundant when transpi- 

 ration is checked by the moisture of the atmosphere. 



99. Natural Order, Pistiacece. — The Duckweed Family. 



Floating herbs, in Lemna consisting of minute, leaf-like 

 fronds. 



Type — Pistta Stratioies. 



A floating herb, with tufted obcordate- 

 cuneate radical leaves, numerous fibrous 

 roots hanging in the water, and minute 

 spathes with adherent spadices rising 

 from the middle of the tuft. 



The annexed cut will explain the in- 

 florescence of Pistia better than a verbal 

 description. The spadix is adherent to 

 the spathe, and terminates in a small 

 head of five adherent four-celled anthers. 

 Immediately below the head of the anthers 

 is the stigma. The ovary is one-celled and ^'/iiv/,viriniongiidinai 

 adherent, containing several ovules. section. 



This little lettuce-like plant is gigantic 



