6 MEMOIRS PROM THE DEPARTMENT OP BOTANY OP COLUMBIA COLLEGE. 



and MiMciihcfJna hwxe their greatest development in the tropics. Besides these two 

 charaeteris^tie distributions there are those genera hke Polygonum and Rumex which 

 flourish from the equator to the arctic zones, that is as far as flowering plants can exist. 



In the second place, in addition to this general distribution of generic areas, there 

 are conspicuous cases of special limitations. For example, we find Eriogonum, one of 

 the larger, and Kcmaccnilis and Centrostegia, among the smaller genera, confined for the 

 most part to Avestern North America, Oxyiheca, Chorizanthe and Pterostegia to the western 

 pcjrtions of North and South Ameria. PolygoneUa and Thysamlla are mainly in the 

 southeastern United States, while Pterococcus and Calliphysa are confined to the plains 

 and mountains of eastern Europe and western Asia. Notwithstanding this general and 

 special variation in latitude and altitude and the broad and restricted geographical ranges, 

 the genera all fall into a remarkably well defined family. 



The name Polygonum is a very ancient derivative, composed of the two Greek words 

 Ttojivg and yovv, meaning respectively many and hiee or joint, alluding to the numerous 

 nodes which are so conspicuous in the stems of many species. It appears to have been 

 associated by the ancient writers with the group to which it was applied by Linnaeus and 

 for which it has since been used. 



With Polygonum aviculare as a basis. Dr. Pickering^ gives the following history of 

 the generic name : Heraclides Tarentina, a Greek physician, who lived in the third and 

 second centuries B. C, is said to have prescribed this plant as a remedy against the flow- 

 ing of blood from the ear. After him other Greek physicians, poets and botanists, such 

 as Nicander, Magnus of Philadelphia and Charixenes seem to have alluded to the plant. 

 The Greek botanist Dioscorides was the first to characterize a form as having "numerous 

 slender branches, creeping on the ground like grass, with fruit at each leaf." Various 

 writers have given the credit of the name to different ancient botanists or pseudo-botan- 

 ists. For example, Pfeiffer^ attributes it to Tournefort, Dietrich^ and Greene* to Co- 

 lumna, and Mueller^ to L'Obel. Linnaeus, who elevated botany into a pure science and 

 -whose time is the turning point from pseudo-botany to real scientific botany, took up the 

 name Polygonum and associated it with the group of plants for which it now stands. At 

 whatever time the historical botanist chooses to start and to whomever he sees fit to refer 

 a genus, the scientific botanist for the sake of avoiding endless confusion and having a sure 

 Ijasis of departure, will not attempt in most instances to seek for names behind the Lin- 

 naean period, certainly not beyond that of Tournefort. 



The first reference we have to Polygonum deals with its real or supposed medicinal 



1 Chrou. Hist. PI. 393. 'Syii. PI. 1319. sgygt. Ceii. Aust. PI. 1 : 31. 



2Nomencl. Bot. 2 : 795. *F1. Francis. 132. 



