126 BRITISH CHAROPHYTA. 



iii 'Bull. Soc. Bot. France/ LII, pp. 88-94 (1905), " Sur le 

 N. confervacea Braun/' with which species he identifies it. 

 iMigula figures the oospore of N. confervacea as lacking the 

 prominent flanged ridges so characteristic of our plant, but 

 in specimens collected by Brebisson, which we have examined,, 

 the ridges are flanged. 



The gelatinous covering to the sexual organs, which gave 

 rise to the specific name, is evidently not a constant character 

 in this species, and if present in the British plant, is very slight. 



N. batrachosperma bears a close resemblance to N. tenuis- 

 sima, but produces reproductive organs at the first furcation, 

 and possesses a granular, not a reticulated, membrane. The 

 number of branchlets in each whorl is usually greater than 

 in N. tenuissima, but they are less repeatedly furcate. It 

 also somewhat resembles a very small and slender con- 

 densed form of N. gracilis, but may be distinguished at once 

 by the uniformly 2-celled ultimate rays. 



In the paper by H. & J. G. in < Journ. Bot.' 1890, p. 66, 

 the name of N. batrachosperma was set aside partly on the 

 theory " once a synonym always a synonym," and partly on 

 the ground of Reichenbach's confused ideas as to his Char a 

 batrachosperma, on which Braun' s N. batrachosperma is based. 

 The theory mentioned, though there is much to be said in 

 its favour, is not in accord with general usage, and since there 

 appears little doubt as to the identity -of the plant described 

 by Reich enbach in the Tl. Germ. Excurs.' and none as to 

 what Braun meant, it is thought best to reinstate the name 

 rather than to use that of N. confervacea published later. 



Of the British Nitellas it is the only species which is not 

 as yet known to occur in England. Its distribution, as at 

 present known, is noteworthy, the five known stations being 

 situated in four widely separated areas. It is scarcely likely 

 that the plant does not occur in some other of the innumer- 

 able lakes that intervene between the north and the south of 

 Ireland, and it may well be expected to occur also in the 

 English and Scottish lakes. 



The plant is by no means an easy one to detect. In its 

 Irish stations it grows in some 4-6 feet of water, beyond the 

 range of vision, and not readily collected by means of a drag. 

 Its discovery is therefore somewhat a matter of chance. 



Subsection 2. Heteroclemse (= Heterophyllds Braun). 

 Whorls compound, having accessory branchlets dis- 

 similar to those of the primary circle. 



