TPIE PURSLANE FAMILY. 447 



cially ; indeed it is questionable whether these natural arrange- 

 ments for securing cross-fertilisation are not themselves the 

 consequence of natural hybridism and selection. 



THE BUCKWHEAT FAMILY (Polygoniacea). 



Annuals, herbaceous plants, or rarely shrubs, distributed 

 throughout Europe, Asia, Africa, and North America. They 

 are also found in South America, the Levant, and one or two 

 species in the most northern limits of vegetation. The prin- 

 cipal genera found in our gardens are JEriagonum, Rheum 

 (Rhubarb), Polygonum, Fagopyrum, Coccoloba, Rumex (Docks 

 or Sorrels), Anttgonum, and others. Many of the species are 

 easily recognised by the coherent membranous stipules, which 

 form an ochreate tube around the stem at the nodes. Nearly 

 all the species produce fertile seeds in great profusion, and the 

 hardy kinds may be sown as soon as ripe, or during the spring 

 months, in a warm sheltered bed or border. Tender kinds 

 should be sown in heat. They are represented by the medi- 

 cinal and esculent Rhubarbs, Polygonums or Buckwheats, 

 and Docks or Sorrels. The hardy Rhubarbs, both useful 

 and ornamental, are readily increased during mild weather in 

 winter by dividing the fleshy crowns and replanting where 

 they are to remain. JR. Emodi and the neAvly - introduced 

 R. nobile from the Himalayas are very effective sub - tropical 

 plants. The Docks are well-known native weeds. The 

 Field -dock (Rumex pratensis, see 'Top. Bot.,' p. 343) is 

 supposed to be a natural hybrid between R. crispus and R. 

 obtusifolius. Several forms are known to occur on the Sheriff- 

 muir Road, near Stirling, West Perth ; and it would be interest- 

 ing to know whether these hybrid plants reproduce themselves 

 from seeds, or whether they are seedlings from one of the last- 

 named species which becomes accidentally fertilised by pollen 

 from the other. 



THE PURSLANE FAMILY (Portulata&fg). 



A small order of succulent shrubs, or more generally herbs, 

 represented in our gardens by Portulaca showy crimson, 

 purple, rose, white, or yellow-flowered plants, with a habit 

 similar to the Fig Marigolds Anacampscros, Calandrinia, 

 Clayton-la, and one or two others. They seed freely if planted 

 in sandy soil and protected from too much damp at the root. 



