114 PUBLIC HEALTH BULLETIN NO. 286 



1. R. fascicvlaris Small — Around ponds and in prairies in peninsular 

 Florida. 



2. R. verticiUatus L. Swamp-dock — Common mostly in swamps of 

 rivers or creeks, various provinces over all of our territory. Laivae 

 of Anojyheles quadrimaculaius have been found associated with this 

 plant. 



2. Polygonum [Toiirn.] L. 



1. Stems armed with prickles; leaves lobed at base 1. P. sagittatum. 



1. Stems not armed with prickles 2. 



2. Stem terminated by a single (sometimes 2) 2. P. coccineum. 

 cluster of flowers; no axillary inflores- 

 cences present. 

 2. Clusters of flowers axillary as well as terminal, 3. 

 more than 2 and usually several. 

 3. Ocreae (sheaths on stem just above bases of leaves) 4. 

 not fringed with bristles. 



3. Ocreae fringed with bristles 7. 



4. Flower clusters erect 5. 



4. Flower clusters nodding, slender 3. P. lapathifolmm. 



5. Plant perennial; achene turgid-lenticular; flowers 4. P. densiflorum. 

 usually white or whitish, with tinj' dark dots when 

 viewed with lens. 

 5. Plant annual; achene flat; flowers usually pink, not 6. 

 dotted. 



6. Style or stamens conspicuously longer than 5. P. longistylum. 

 the perianth. 



6. Style or stamens hidden by the perianth 6. P. pensylvanicuni . 



7. Perianth showing tiny dark dots when viewed with a 8. 



lens. 

 7. Perianth not showing tiny dark dots when viewed 9. 

 with a lens. 



8. Achene granular, dull; flower clusters often 7. P. hydropiper. 



nodding. 

 8. Achene smooth, shining; flower clusters erect- 8. P. punclatum. 



9. Flower cluster short, stout, compact 9. P. persicaria. 



9. Flower cluster slender, not dense 10. 



10. Leaves cordate or subcordate at base, sessile; 10. P. hirsutum. 



stem and ocreae hairy. 

 10. Leaves narrowed to a petiole at base; stem 11. 

 and ocreae not hairy. 

 11. Leaves tapering to both ends from a point well below 11. P. setaceum. 

 the middle covered with stiff" hairs. 



11. Leaves with nearly parallel sides usually not hairy 12. 



12. Spike loose; the white or pink perianth com- 12. P. hydro piperoides. 



pletely hiding the mature nutlet. 

 12. Spike more dense; the green perianth not 13. P. opelousanum. 

 hiding the tip of the mature achene. 



1. P. sagittatum L. Rakestraw — Moist places over all of our terri- 

 tory. 



2. P. coccineum Muhl. — Occurs widely in our territory, but infre- 

 quent. Seems to prefer alluvial situations. This and the following 

 11 species are listed under the genus Persicaria by Small. 



