KNOTWEED FAMILY 



351 



4. POLYGONUM. Knotweed. Smahtweed. 



Low weedy plants, or some exotic ones tall and cultivated, blooming in 

 summer and fall, the small pinkish or greenish flowers mostly in racemes or 

 spikes (in the Knotweeds in the leaf-axils): calyx usually 5-parted: stamens 

 4-9: stigmas 2 or 3: black achene lenticular or triangular. 



a. Knotweeds: /lowers sessile in the axils of the leaves, greenish and very small. 



P. aviculare, Linn. Common knotweed. Doorweed. Fig. 210. Pros- 

 trate or creeping, bluish green wiry plant, growing along the hard edges of 

 walks and in yards, and commonly mistaken for sod: leaves small, mostly 

 oblong, entire: sepals very small, green with a broad white margin: stamens 

 5 or more: stigmas usually 3. Annual. 



P. erectum, Linn. Taller knotweed. One ft. or more high: leaves three 

 or four times larger, oblong or oval and obtuse. Common annual. 



aa. Smarhveeds: flowers in terminal spikes, mostly pinkish. 



b. Sheaths of leaves (surrounding stem) hairy on the edge, or 



the margin with a spreading border. 



P. orientate, Linn. Prince's feather. Several feet tall, soft- 

 hairy: flowers in long cylindrical nodding spikes: leaves ovate: 

 stamens 7. India; cultivated. Annual. 



P. Persicaria, Linn. Smartweed. Lady's thumb (from the 

 dark blotch near the center of the leaf). Fig. 514. About 1 

 ft.: leaves lanceolate: spikes oblong, dense and erect: stamens 

 usually 6: stigmas 2. Weed from Europe. 



P. Hydropiper, Linn. Smartweed. Herbage very pungent 

 or "smarty:" leaves oblong-lanceolate: spikes short and 

 nodding, the flowers greenish: stamens 6: stigmas 3. Low 

 grounds. Annual. 



P. hydropiperoides, Michx. Smartweed. Herbage not 

 pungent: spikes slender and erect, the flowers whitish: sta- 

 mens 8: stigmas 3. In very wet places. Perennial. 



P. acre, HBK. Smartweed. Herbage pungent: leaves 

 linear or lanceolate, long-pointed: spikes slender and erect: flowers white or 

 blush: stamens 8: stigmas 3. Low grounds. Perennial. 



bb. Sheaths of leaves not hairy, nor the margin bordered. 

 P. pennsylvanicum, Linn. Smartweed. Pungent: plant with conspicuous 

 glandular hairs above: leaves lanceolate: spikes short-oblong and erect, the 

 flowers purplish: stamens 8: stigmas 2. Low ground. Annual. 



XIII. EUPHORBIACE.E. Spurge Family. 



Trees, shrubs or herbs, often with milky, pungent juice, some- 

 times poisonous: flowers monoecious or dioecious, mostly apetalous, 

 usually small and inconspicuous. The family is large, in wanner parts 



