1863.] PONDWEEDS. 459 



after Thcophrastus, does mentiou in his 4th book and 96th 

 chapter^ one species of Potamogeton, viz. P. nutans, and he is 

 followed by Pliny, who copies verbatim his learned Greek prede- 

 cessor. The description given by the latter in his 26th book and 

 33rd chapter is almost identical with that of Dioscorides. Let 

 the learned reader compare the descriptions or notices of the 

 plants given us by these two ancient historians, and he will see 

 their coincidence. 



The following is quoted verbally from the new translation of 

 Pliny, vol. v. p. 172, H. G. Bohn's edition : — " Potamogiton . . . 

 is a plant similar to Beet in the leaves, but smaller and more 

 hairy, and rising but little above the surface of the water." The 

 eminent commentator on Dioscorides gives the following version 

 of his author's text, loco citato, p. 713, ed. 1570: — "Potamo- 

 geton folium fert betse simile, hirsntum, paululum supereminens 

 extra aquam." 



Pliny adds, " Castor has given a different description of this 

 plant. According to him, it has a smaller leaf, like horsehair, 

 with a long smooth stem, and grows in Avatery localities." (Book 

 26, c. 33, vol. V. p. 173, as above.) 



Billerbeck (' Flora Classica,' p. 37) makes the first species P. 

 natans, and the second P. pectinatum. It may be said that nei- 

 ther of these species agree exactly with Pliny's description. 



This would be a puzzle to the modern readers of Pliny and 

 Dioscorides, to learn why these authors call the Potamogetons 

 hairy plants, hairier than Beet, if they did not know or were not 

 told that the plant described by these eminent botanists is not a 

 Potamogeton, but Polygonum amphibiuin. This is a hairy-leaved 

 plant, whether it grows in the water, or on land not far from 

 water; but in the latter it is remarkably hairy. We are in- 

 debted to the learned and observant Ray for the rectification of 

 this ancient error. The floating or aquatic Persicaria, in early 

 summer, ere it has thrown up its handsome spike of rose-co- 

 loured flowers, might be, at a distance, easily mistaken for lan- 

 ceolate-leaved forms of Potamogeton natans. 



Can any reader inform us if any of the more recent editors of 

 Dioscorides and Pliny have anywhere pointed out this mistake 

 and traced its origin ? 



Every botanist knows that the Pondweeds (Potamogetons) are 

 not hairy, and also that Beet is not hairy ; yet both Dioscorides 



