142 Rhodora [Auausr 
wet sandy shore of Sheep Pond, Brewster, July 4, 1911, F. S. Collins, 
no. 1,184, July 11, 1918, Fernald, no. 16,753; sandy beach of Cliff 
Pond, Brewster, August 27, 1918, Fernald & Long, no. 16,757; wet 
sandy beach of Long Pond (east of Cliff Pond), Brewster, August 27, 
1918, Fernald & Long, no. 16,758; wet sandy lower beach of second 
pond north of No Bottom Pond, Brewster, September 7, 1918, Fernald 
& Long, no. 16,760; lower damp sandy beach of Griffith’s Pond, 
Brewster, September 12, 1918, Fernald, no. 16,761; sandy shore of 
pond, Eastham, August 8, 1907, F. S. Collins, no. 425. 
Related on the one hand to P. Persicaria L., on the other to P. 
minus Hudson. P. Persicaria has thicker spikes, the mature primary 
ones 7-11 mm. thick; larger flowers and achenes, the achenes 2.5-3 
mm. long, and often slightly exserted at maturity; and in the mature 
perianth the lower half of the segments is usually reticulated or 
strongly nerved. Besides these more constant characters there are 
others less pronounced: when well developed P. Persicaria is a much 
coarser plant and the primary leaves may become 2-4 cm. wide; in 
P. Persicaria, also, the pedicels are inclined to be more exserted, 
though this character is not a reliable one. 
P. puritanorum in its smooth small perianth and small achene is 
nearer to P. minus than to P. Persicaria. P. minus, however, has 
decidedly less rhombic-lanceolate leaves, its primary leaves being 
lanceolate or linear-lanceolate to narrowly oblong; the spikes of P. 
minus are extremely slender and loosely flowered, much as in P. 
Hydropiper; and the achenes are ovate rather than ovate-orbicular. 
Gray HERBARIUM. 
