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 



5. sagittcefolia, L., Arrow-head ; ditches ; Switzerland, 

 rare. 



3. BUTOMUS, L. 



Flowers bisexual, in umbels subtended bjran 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 (Bile). 



Order XCII.— 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. siinplex, Huds.; 

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

 natans, Koch, zxid: affihe, Schn.); stem and leaves float- 

 ing ; not so common. 



