164 THE FLORA OF THE ALPS 
2. SAGITTARIA, L. 
Flowers unisexual, in whorls; sepals green; petals 
white; stamens numerous; leaves erect, arrow-shaped, 
thick, very shining 
S. sagittefolia, L., Arrow-head; ditches; Switzerland, 
rare. 
3. BUTOMUS, L. 
Flowers bisexual, in umbels subtended by an involucre ; 
sepals and petals pink; stamens 9; carpels 6. 
B. umbellatus, L., Flowering Rush; stem 6-12 in., 
flowers I in. diameter, leaves linear, erect; ponds and 
streams ; very rare (Bale). 
Order XCII.—TYPHACE. 
Flowers monececious, in globular or cylindrical spikes 
or heads; perianth reduced to membranous scales or 
hairs; ovary I-celled, with usually one pendulous ovule; 
leaves narrow, with sheathing base; root-stock a creeping 
rhizome. Aquatic or marsh plants. 
I. SPARGANIUM, L. 
Heads globose, subtended by leafy bracts; perianth of 
3-6 membranous scales ; fruit a small I-2-celled drupe. 
S. ramosum, Huds., Bur-Reed; stem erect, branched, 
leaves triquetrous ; ditches, common. SS. szmplex, Huds.; 
stem erect, simple; and S. mznzmum, Fr. (including ~ 
natans, Koch, and affine, Schn.); stem and leaves float- 
ing; not so common. 
