102 BRITISH CHAROPHYTA. 



N. flexilis. Extreme forms of the apex will be seen in 

 PI. VI, figs. 3-7. 



N. opaca is variable in habit. In its typical form it is 

 a stout close-growing plant with rather short branchlets 

 and dense fruiting heads. In marked contrast to this, the 

 var. attenuata has long and very delicate branchlets, and 

 the fruiting whorls, which are lax and spreading, are little 

 distinguishable from the sterile whorls. 



Small tufted forms sometimes occur on the sandy bottoms 

 of lakes. The Llyn Idwal form, already referred to under 

 N. capillaris, is very small (about 15 cm. high) and remark- 

 ably slender, and the fruiting heads are small. Occasionally 

 the fruiting branches are very short and the heads diminutive. 

 An extreme form of this variation was collected by G. R. B.-W. 

 at Little Sea, Studland, Dorset. 



It is by far the commonest of our Kitellas, to be found 

 almost everywhere, occurring even in slightly brackish 

 water. It also reaches a higher elevation than any of the 

 others, having been collected in Perthshire at 3100-3300 feet. 



This species was confused by many of the earlier writers 

 with the allied species N. syncarpa, already referred to. It 

 appears under the name C. syncarpa, up to the 7th ed. of 

 Babington's 'Manual/ and specimens have in consequence 

 been largely so labelled in British herbaria. 



Var. b. attenuata. 



Geovbs in Journ. Bot. XIX, p. 356 (1881) ; Exsicc. 29. 



Branchlets very long, often equalling in length tlie 

 internodes of the stem, extremely slender; secondary 

 rays about as long as the primary. Fertile ivhorls lax. 



Hants, S., in a pond on Beaulieu Heath, near Hythe 

 (first foxmd in 1878 by E. Groves) ; Dorset, Little Sea 

 {G. E. B.-W. 1903). 



3. Nitella flexilis Agardh. 

 (Plate VIII.) 



Chara flexilis Linn. Sp. Plant, p. 1157 (1753), ex parte. 

 SCHKTTHE Bot. Handb. Til, p. 219, t. 280 (1808). 

 Bettzblitjs Obs. Char. pp. 15, 23 (1824). 



Beattn in Ann. Sc. Nat. ser. 2, I, p. 351 (1834) ; in Flora, XVIII, i, 

 p. 50 (1835). 



