1 64 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 



6^. sagittcefoliay 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 XCH.— TYPHACE^. 



Flowers monoecious, 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 1-2-celled drupe. 



6". ramosum, Huds., Bur- Reed; stem erect, branched, 

 leaves triquetrous; ditches, common. S. simplex, Huds.; 

 stem erect, simple ; and S. miniimim, Fr. (including 

 natanSy Koch, and affine, Schn.); stem and leaves float- 

 ing; not so common. 



