POLYGONACE^ 



123 



Broad Dock — Rumex obtusifolius 

 (Plate LXXXII) 



The different species of Dock and Meadow 

 Sorrel belonging to the genus Rumex are very 

 similar, and several are very common in Britain, 

 either in fields, like the present species, or in 

 swampy places. The Broad Dock grows 2 or 

 3 feet high, and the stems, flowers, and leaf-veins 

 are reddish. Several other species are more or 

 less red, like this ; but others are green. The Great 

 Water-Dock {Rumex hydrolapathum) is common 

 in fenny districts, and grows to the height of 5 or 

 6 feet. The leaves of the species of Rumex are 

 very succulent, and those of two small meadow 

 species {Rumex acetosa and R. acetoselld) have a 

 pleasant acid flavour when chewed, and are called 

 Meadow Sorrel, or Sheep's Sorrel. 



The green wood-louse shaped caterpillars of 

 the Copper Butterflies feed on Dock. The Small 

 Copper {Lyazna phlceas) is still common ; it is 

 bright coppery-red, with black spots, and measures 

 an inch and a quarter across the wings. The 



Large Copper [Lyccena dispar), more than twice 

 the size, with fewer black spots above, and the 

 hindwings blue beneath, which used to feed on the 

 Great Water-Dock in the Fens, was exterminated 

 by the draining of the Fens about sixty years ago. 



Knot-grass — Polygonum aviculare 

 (Plate LXXXII I) 



The species of Polygonum are straggling plants, 

 with slender hollow stems with numerous knots 

 and simple alternate leaves. The small flowers 

 grow in whorls and clusters. Some of the species, 

 like that figured, are found in dry fields, and are 

 troublesome weeds ; others grow in swampy places, 

 or by the sea-shore. This plant is so great a 

 favourite with caterpillars that it is a rule among 

 entomologists to offer it to any caterpillar about 

 the food of which they are uncertain ; and in many 

 cases it is accepted, and the insects are reared 

 upon it without difficulty. 



Among cultivated plants of this Order we may 

 mention the Rhubarbs and the Buck-wheat. The 



