POLYGONACE^ (BUCKWHEAT FAMILY.) 



701 



Var. Iietcraiitlia, Boiss. Some of the flowers (ofteu iii the 

 same recemc), 4-merous, with flat akene, others 5-merous, with triciuc- 

 trous akeuc — Same range as last; also Aintab and Sof Dagh. 



T. POLYOONUIfl, L. Knotweed. 

 Flowers perfect. Perigonium 4-5-cleft or -parted, herbaceous or 

 petaloid, persistent, enclosing the fruit. Stamens 4-8, in two rows, 

 inserted at base of perigonium. Styles or stigmas 2-3. Akene trian- 

 gular or lenticular, crustaccous, with erect seed. Embryo accumbcnt 

 to angle of albumen, or curved and somewhat immersed, with leafy 

 cotyledons and superior radicle — Annual or perennial herbs or shrubs, 

 with the base of the petiole expanded into a membranous, tubular 

 sheath {ochreoi), and membranous, interfloral bracts (ochreoles). 



Fm. 331. 



d c a h ■ 



(a) Tip of a flowering brancli of a Polygonum, showing the ochrete, leaves, and spikes 

 of flowers, (b) A single flower, showing the 4 lobes of perigonium with stamens inserted 

 at their base, and the free ovaiy with two styles, connate at base, (c) Vertical section of 

 ovary, showing the erect ovule, (d) Vertical section of seed, showing tlie lateral embryo. 



='■' SpiJce 1, at tip of simple stein. Styles 3, free, loith small stigmas. 

 Stamens 5-8. Ochrecc oUique, not ciliate. 



1 P. Bistorta. 



* * Stems usually hrancKing, sjjikes at end of branches. Styles 2-3, more 



or less connate. Stamens 8-4, loith alternate scales. Oclirecti cylindrical, 



tisiudly ciliate. 



t Perennials. Flowers in 2 pentandrous, in 3 liexandrous. 



2 P. amphibium, 3 serrulatum. 



