258 Minnesota Plant Life. 



weeds. The smallest of the docks has spear-head shaped leaves 

 and is known as sorrel. The other docks are some of them 

 large-leaved plants most luxuriant in marshes or swamps. 

 Among them are the water-, the swamp-, the yellow, the golden, 

 the red-veined, the pale, and the curly-leaved docks, differing 

 principally in leaf characters. The only one in Minnesota with 

 sour leaves is the sorrel, and on account of this pleasant acid 

 taste the leaves are often picked and eaten. These sorrels are 

 not to be confused with the sheep-sorrel, in w r hich the leaves are 

 shaped like clover leaves, an entirely different kind of plant. 

 The different species of dock, besides by their leaf characters, 

 are to be distinguished by the wings on the fruits. 



The smartweeds, knotweeds, or bindweeds fall into three 

 groups of species; some, in which the leaves are shaped like 

 those of the willow, others, in which the leaves are small and 

 slender, and still others with heart-shaped or arrow-shaped 

 leaves and twining or climbing stems. The forms with willow- 

 shaped leaves are known under the general name of smartweeds ; 

 those with the small leaves are called knotweeds, jointweeds, 

 knot-grass or doorweeds, while those with arrow-shaped or 

 heart-shaped leaves are termed bindweeds, false buckwheat or 

 tear-thumbs. They are all similar in the structure of their flow- 

 ers and fruits. One variety, the water-smartweed, produces its 

 stem under the water and sends its leaves to the surface, where 

 they float like the leaves of the pond-lily. The flowers are 

 clustered in bright pink spikes thrust above the surface of the 

 water. Another kind with similar habit is found as a surf-plant 

 in northern lakes. The ordinary smartweeds grow in moist 

 soil and ditches, where their bright pink or red spikes of flowers 

 are conspicuous objects. The knotweeds are common mat- 

 plants of dooryards. In most of the varieties stipules at the 

 bases of the leaves coalesce and form tubular sheaths around 

 the stem. The bindweeds or false buckwheats occur either as 

 twining vines with heart-shaped leaves and flowers like those 

 of the buckwheat, or they grow with slender erect stems reclin- 

 ing against the vegetation near them and supporting them- 

 selves by sharp recurved prickles. These. are known as tear- 

 thumbs, and belong to a small adaptational group of hook- 

 climbing plants. 



