74 



SPARGANIACEAE. 



13. Sparganium minimum Fries. 



Fig. 173. 



VOL. I. 



Small Bur-reed. 



Sparganium natans Oeder. Fl. Dan. 2 5 : 5. 1764. Not S. natans 



L. 1/53- 



Sparganium minimum Fries, Sunima Veg. Scand. 2: 560. 1849. 

 Sparganium angustifoliitm A. Gray, Man. Ed. 5, 430. 1856. Not 



5". angustifolium Michx. 1803. 



Stem floating and sometimes elongated, or decumbent, as- 

 cending or erect, and relatively short; leaves dark-green, nar- 

 row, mostly l"^3l" wide, flat; upper leaf-sheaths somewhat 

 dilated, but not scarious-margined ; pistillate heads solitary, 

 or 2 or 3 and placed about equally distant, axillary; fruiting 

 heads about 5" in diameter; nutlets greenish-brown, dull, the 

 body broadly ellipsoid, usually constricted below the middle; 

 stigma obliquely oblong or oval. 



In ponds and streams, Labrador to Alaska, New Jersey, Ten- 

 nessee ( ?), Utah and Oregon. Also in Europe and Asia. June-Aug. 



Family 3. ZANNICHELLIACEAE Dumort. Anal. Fam. 61. 1829.* 



PONDWEED FAMILY. 



Perennial marine or fresh-water plants with floating or submerged leaves, or 

 both. Leaf-blades petioled or sessile, capillary or expanded into a proper blade, 

 or rarely reduced to terete phyllodes. Flowers perfect or monoecious, in sessile 

 or peduncled spikes, or in clusters in the axils of the leaves. Perianth none, but 

 flowers sometimes enclosed in a hyaline sheath. Androecium of 1-4 stamens. 

 Anthers extrorse, i-2-celled, the connective sometimes becoming perianth-like. 

 Gynoecium of 1-4 distinct, i-seeded carpels. Fruits mostly nut-like or drupe- 

 like, sessile or stipitate. Endosperm wanting. 



About 4 genera and 70 species of wide geographic distribution, most abundant in temperate 

 regions. The months noted in the descriptions indicate the fruting period. 



Flowers perfect ; stamens more than i. 



Stamens 4 ; fruit sessile. 



Stamens 2 ; fruit stalked. 

 Flowers monoecious; stamen i. 



1. Potamogeton. 



2. Ruppia. 



3. Zannichellia. 



i. POTAMOGETON L. Sp. PI. 126. 1753. 



Leaves alternate or the uppermost opposite, often of 2 kinds, submerged and floating, 

 the submerged mostly linear, the floating coriaceous, lanceolate, ovate or oval. Spathes 

 stipular, often ligulate, free or connate with the base of the leaf or petiole, enclosing the 

 young buds and usually soon perishing after expanding. Peduncles axillary, usually emersed. 

 Flowers small, spicate, green or red. Perianth none. Stamens 4. Anthers sessile, the con- 

 nective dilated, perianth-like (Fig. 186). Ovaries 4, sessile, distinct, i-celled, i-ovuled, atten- 

 uated into a short erect or recurved style, or with a sessile stigma. Fruit of 4 ovoid or sub- 

 globose drupelets, the pericarp usually thin and hard or spongy. Seeds crustaceous, campylo- 

 tropous, with an uncinate embryo thickened at the radicular end. [Greek, in allusion to the 

 aquatic habitat.] Water Spike. 



About 65 well-defined species, natives of temperate regions. Besides the following, about 3 

 others occur in the southern parts of North America. Type species Potamogeton natansL. 



Stipules axillary and free from the rest of the leaf. 

 With floating and submerged leaves. 

 Submerged leaves bladeless. 

 Nutlets more or less pitted. 

 Nutlets not pitted. 

 Submerged leaves with a proper blade. 



Submerged leaves of 2 kinds, lanceolate and oval or oblong 

 Uppermost broadly oval or elliptical, lowest lanceolate. 



Uppermost lanceolate and pellucid, lowest oblong and opaque. 4. P. pulcher. 

 Submerged leaves all alike, capillary or linear-setaceous. 



i-nerved or nerveless. 25. P. VaseyL 



3-nerved. 26. P. laicraiis. 



Submerged leaves all alike, linear. * 



15 Text of this family and of the two following ones contributed to the first edition by 

 the late REV. THOMAS MORONG, revised for this edition by MR. NORMAN TAYLOR. 



1. P. natans. 



2. P. Oakcsianus. 



3. P. amplifolius. 



