BUR-REED FAMILY 301 



2. Leaves 4-1 2 mm. wide; spikes light brown; stam- 



inate and pistillate parts usually separate, 4-15 



mm. wide ; stigmas linear to linear-oblong T. angustifolia 



SPARGANIACEAE BUR-REED FAMILY 



Sepals and petals reduced to a few chaffy scales, stamens usually 5, 

 filaments distinct, ovary usually 1-celled, fruit nut-like ; flowers monoecious, 

 densely crowded in round heads, staminate heads above, spathes linear, just 

 below or some distance below the heads ; marsh or aquatic plants with 

 creeping rootstocks, erect or floating stems, and alternate, linear, sheathing 

 leaves. 



Sparganium Linne 1753 Bur-reed 

 (Gr. sparganon, band, from the ribbon-like leaves) 

 PI. 44, fig. 4. 

 Characters of the family. 



1. Nut-like fruits sessile, angled; fruiting heads 2- 



3 cm. wide 5*. euryedrpum 



2. Nutlets stalked, round or spindle-shaped; fruit- 



ing heads 4-20 mm. wide 



a. Flower cluster branched; fruiting heads 1-2 



cm. wide S. androcladum 



b. Flower cluster simple 



(1) Staminate heads 4-6, pistillate heads 2-6, 



the latter 10-15 mm. wide in fruit S. simplex 



(2) Staminate heads 1-2, pistillate heads 1-3, 



the latter 4-10 mm. wide in fruit S. minimum 



NAIADACEAE PONDWEED FAMILY 



Sepals and petals, or perianth, 4 or none, stamens usually 1-4, pistils 

 1-9, ovary 1-celled, carpels usually 1-seeded, rarely splitting; flowers per- 

 fect, monoecious or dioecious, axillary or in spikes ; aquatic plants with 

 submerged leafy stems and alternate or opposite leaves. 



1 . Leaves alternate ; flowers perfect ; stamens 2 or 4 



a. Perianth of 4 parts Potamogeton 



b. Perianth none Ruppia 



2. Leaves mostly opposite or clustered ; flowers 



monoecious or dioecious; stamen 1 



a. Leaves entire; flowers clustered Zannichellia 



b. Leaves spiny-toothed ; flowers solitary Naias 



