oyO SIUM. [CLASS V. ORDEK II. 



Habitat. — Ditches and vivulets ; frequent in England and Ireland ; 

 but not common in Scotland. 



Perennial ; flowering in July and August. 



GENUS LXI. SI'UM Linn. Water Parsnip. 



Gen. Char. CaZy.!; margin of fi\e teeth. Pete/s obcordate, with an 



inflexed point. Fruit laterally compressed or contracted. Dish 



flattish, with a depressed margin. Stijles reflexed. Carpels with 



five equal obtuse filiform ridges, the lateral ones forming the 



margins. Channels with three superficial vittce. Albumen 



rounded at the back, flat in front. General involucre mostly 



of several linear segments, partial of numerous ones. — Name from 



cnu, to move ; from the plant being almost constantly agitated 



by the water: or, according to Theis, from the Celtic word siw, 



water. 



1. S, lati'folium, Linn. (Fig. 434.) broad-leaved Water Parsnip. 



Stem erect ; leaves pinnated ; leaflets lanceolate, equally and acutely 



serrated; umbels terminal ; involucre of numerous linear segments. 



English Botany, t. 204. — English Flora, vol. ii. p. 56. — Hooter, 

 British Flora, vol. i. p. 130. — Lindley, Synopsis, p. 121. 



Moot of slender long branched fibres, from the creeping underground 

 stem. Flowering stems erect, angular, smooth, deeply furrowed, from 

 two to six feet high, smooth, hollow, branched, and leafy. Leaves 

 alternate, pinnate, on long striated footstalks, with a dilated base, with 

 membranous edges sheathing the stem, the lower ones or those under 

 the water sometimes bi-pinnate, with the margin of the leaflets irre- 

 gularly cut and serrated, the upper ones with about five pairs, and an 

 odd one of lanceolate smooth leaflets, of a lively green above ; beneath 

 paler, somewhat glaucous, with a mid-rib and numerous fine netted 

 veins, the margin fine, and acutely serrated. Umbels teiminal, large, 

 of numerous long angular rays, of nearly equal lengths, partial of 

 numerous short slender nearly equal ones. General involucre mostly 

 of several linear reflexed segments, sometimes one or two of them 

 pinnated, partial of several lanceolate mostly unequal ones. Flowers 

 white, crowded. Calyx of five teeth, sometimes very small. Petals 

 inversely heart-shaped, or obcordate, with an inflexed small point. 

 Stamens with slender filaments, and rather large inversely heart- 

 shaped anthers, of a purplish colour. Styles short, reflexed, or 

 spreading. Stigmas small, obtuse. Disk flattish, with a depressed 

 margin, fleshy, yellowish, crowning the oy&ie fruit, with the sides much 

 compressed or contracted, smooth. Carpels with five filiform obtuse 

 palish equal ridges, the lateral ones forming the margins. Channels 



