TETRAND. TETRAG. ,59 



HAB. Ditches and ponds, not very common, Light/. In the Clyde, 



Ure. Fl. Aug. I/ . 

 Not being- acquainted with this, as really distinct from the preceding, 



I quote Smith's description. 1 should doubt its being a good 



species. 



1 1. P. pusillum (small Pond-weed], " leaves linear opposite and 

 alternate distinct spreading from the base, -stem cylindrical" 

 (Sm.). Lightf. p. 124. E. B, t. 215. 



HAB. Ditches and stagnant waters, Lightf. Common, Hopk. Fl. 

 July. 2/ . 



Having no authentic specimens of this species in my possession, 

 I can add nothing from my own observation to the above charac- 

 ter from Smith. 



12. P. pectinatum (fennel-leaved Pond- w eed), leaves distichous 

 setaceous alternate sheathing, stipules scarcely any, spike of 

 flowers interrupted. Lightf. p. 123; and p. \24(P.marinum). 

 E. B. t. 323. 



HAB. Rivers, lakes and salt-water ditches. Lake of Rescalin, near 

 Forfar, D. Don. River Tweed, near Kelso, Maugh. 



This species, from the leaves being rather closely set and regularly 

 distichous, has, when growing, a remarkably pectinated appear- 

 ance. Sheaths of the leaves long. The spike is interrupted, and 

 as well as the general habit not unlike Ruppia maritima. 



15. RUPPIA. 



1. R. maritima (Sea Ruppia]. Lightf. p. 124. E. B. t. 136. 



HAB. Stagnant waters by the sea-side, not uncommon, as at Glen- 

 Elg, Inverness-shire, Lightf. Salt-water pools at Guillon Links, 

 Edinb., Maugh. Aberlady Bay, Mr. Arnott. FL July, Aug. I/.. 



Stems slender, filiform, flexuose, branched, leafy. Leaves linear- 

 setaceous, sheaths an inch long, membranaceous, inflated. Spadix 

 at first very short, included in the sheaths, with 2 naked green flow- 

 ers one above the other, on opposite sides. Anthers large, sessile, 

 subquadrate, bursting horizontally. Germens resembling 4 minute 

 tubercles in the centre between the anthers. After flowering, the 

 spadix lengthens remarkably, five or six inches or more, and be- 

 comes spirally twisted, so that it may extend or contract itself with 

 the rising or falling of the waters ; at the same time the germens 

 swell, and rise upon footstalks (as the fruit ripens) of an inch in 

 length. Drupes 4, ovate, acuminate. For a more full account than 

 I am able to insert here of this highly curious plant, and a full ana- 

 lysis of the parts of fructification., I must refer to the New Series 

 of the Flora Londinensis. 



16. SAGINA. 



1. S. procumlens (procumbent Pearl-wort], perennial glabrous, 

 stems procumbent, leaves shortly mucronate, petals much 

 shorter than the cal., caps, longer than the cal. Lightf. p. 

 125. E.B.I.S80. 



HAB. Sandy and gravelly soils, frequent. Fl. June, July. I/. 



