PUANTS OF SOUTHERN NEW JERSEY. i6i 



c. Leaves crowded on the branches 12-25 mrn- long. 1-2 mm, wide. 



Najas flexilis^ p. 165 

 cc. Leaves capillary opposite or in whorls 12-50 mm. long. 



Najas gracillima, p. 166 

 bbbb. Fruit sessile in a cluster or short spike borne on a common peduncle 

 or rarely sessile. 



c. Stem much branched above, the branches continually forking; 

 fruits smooth and plump, in an elongated spike. 

 d. Fruit 2-3 mm. long in a compact spike. 



Ptamogeton confervoides, p. 163 

 dd. Fruit 3-4 mm. long in an interrupted spike, in whorls. 



P. pectinatus, p. 164 

 cc. Stem densely dichotomously branched above. 



d. Fruit smooth and plump, in a cluster of 3-10, about 2 mm. 



long. P. pusillus, p. 164 



dd. Fruit flattened with a prominent spiral ridge on the side 



(sometimes with oval floating leaves and pedicelled spikes 



projecting from the surface). 



e. Submerged spikes sessile, i-io fruited, fruit less than 



2 mm. in diameter. P. dimorphus, p. 164 



ee. Submerged spikes, short pedicelled, i mm. in diameter. 



P. diversifoliiis, p. 164 

 aa. Leaves ovate, elliptical or oblong lanceolate. Fruits in a dense spike, 

 supported on a peduncle. 

 b. All submerged. 



c. Cordate clasping or perfoliate. P. perfoliatus, p. 163 



cc. Sessile, with margins finely serrulate and crisped. 



[P. ci'ispus]* 

 bb. Some leaves floating petioled thicker and more curiaceous than the 

 thin submerged leaves. 

 c. Floating leaves ovate or round ovate, 50-100X30-50 mm. 



d. Snbmerged leaves large elliptic. P. amplifolius, p. 162 



dd. Submerged leaves lanceolate, acuminate. P. pulcher, p. 162 

 cc. Floating leaves 12-30 mm. wide. Elliptic or obovate. 



d. 25-50 mm. ; submerged leaves capillary, root like. 



P. oakesianus, p. 162 

 dd. 35-85 mm. long, somewhat obovate, obtuse ; submerged 

 leaves linear, closely ranked, 5-15 cm. long. 



P. epihydrus, p. 162 

 ddd. 50-150 mm. long, pointed at each end; submerged leaves lan- 

 ceolate acuminate 10-30 cm. long. P. americanus, p. 163 

 ccc. Floating leaves elliptic obtuse, not over 25X12 mm., usually one- 

 third less. Submerged leaves narrowly linear grass-like. 



d. Submerged fruit clusters sessile. P. dimorphus, p. 164 



dd. Submerged fruit spikes short pedicelled. 



P. diversifoliiis, p. 164 



* Introduced in ponds and ditches. 

 TI MUS 



