96 BOTANY OF MICHIGAN 



partially shaded ground. Common. By some authors included in C. 

 umbellata (L.) Nutt. 



Comandra Uvida Richards. Northern comandra. In dry sterile open 

 or shaded ground. Apparently infrequent. 



LORANTHACEAE. Mistletoe Family 



Arceuthobium pusillum Peck. (Razoumojskyo, pusilla (Peck) Kuntze). 

 Dwarf mistletoe. Parasitic on the twigs of white spruce and black spruce 

 causing them to curl up into thick bunches, forming what are called 

 "witches' brooms. " Frequent. 



POLYGONACEAE. Buckwheat Family 



Rumex britannica L. Great water dock. In wet marshy places 

 throughout. Common. 



Rumex crispus L. Yellow dock. About cities and villages and in 

 cultivated grounds. A miserable weed. 



Rumex mexicanus Meisn. Willow-leaved dock. Sandy beaches of 

 Lake Michigan and in dry open ground throughout. Frequent. 



Rumex ohtusifolius L. Bitter dock. Frequent in cities, villages, and 

 cultivated grounds as a weed. 



Rumex acetosella L. Field sorrel. Common in cultivated grounds. 



Polygonum aviculare L. Knot-grass. Common about cities and vil- 

 lages, in lawns, gardens, and other cultivated grounds. 



Polygonum erectum L. Erect knotweed. Mostly about cities and vil- 

 lages, and on roadsides as a weed. Frequent. 



Polygonum lapathifolium L. (Persicaria lapathifolia (L.) S. F. GrajO- 

 Pale persicaria. In damp open ground. Noticed mostly as an occa- 

 sional weed about cities and villages. 



Polygonum amphibium L. {Persicaria amphibia (L.) S. F. Gray). 

 Water persicaria. Margins of ponds, small lakes, and along low banks 

 of streams. Plentiful. 



Polygonum muhlenbergii (Meisn.) Wats. (Persicaria muhlenbergii (S. 

 Wats.) Small.). Swamp persicaria. Marshy and swampy places, mar- 

 gins of ponds and along streams. Often in shallow water. Common. 



Polygonum hydropiper L. (Persicaria hydropiper (L.) Opiz.) Smart- 

 weed. In damp open or partially shaded ground. Plentiful. 



Polygonum acre HBK. (Persicaria punctata (Ell.) Small.). Water 

 smart weed. Wet marshy ground and along low banks of streams and 

 occasionally in shallow water. Plentiful. 



Polygonum persicaria L. (Persicaria persicaria (L.) Small.) Lady's 

 thumb. Usually in damp open places as a weed in cities and villages. 

 Frequent. 



Polygonum sagittatum L. (Tracaulon sagittatum (L.) Small.). Arrow- 

 leaved tear-thumb. Damp open or partially shaded ground. Frequent. 



