BATRACHOSPERMUM. 113 



the joints among the whorls of eccentric filaments, and are 

 themselves beset with whorls ; colour grey." 



10. BATRACHOSPERMUM RUBRUM Hass. 

 Plate XV. Figs. 2, 3. 



Char. Filaments much branched. Branches divaricate, alter- 

 nate, ramuli broad, expanded. Whorls of the stems sphe- 

 rical, distinct, subdistant, large, those of the branches 

 altogether confused. 



Batrachospermum moniliforme var., Penzance, June, 1839 : 

 Mr. Ralfs. 



This is one of the most curious, at well as distinct species 

 of the genus. I have seen but a single specimen of the 

 plant, but this is quite sufficient to establish it as a species. 

 This specimen was sent to me, amongst other good things, by 

 my friend Mr. Harvey, and belongs to the Herbarium of 

 Trinity College, Dublin, to which Mr. Harvey, I believe, 

 has generously presented the whole of his collection of Algae. 



Batrachospermum rubrum might possibly be mistaken for 

 Thorea ramosissima, on account of its mode of ramification, its 

 colour, which is bright red, and, above all, the expanded 

 branches, which are so like those of T. ramosissima, that if 

 it were not for the whorls on the main stems, the species 

 might readily be referred to the genus Thorea, an error 

 which even a microscopic examination of the plant would not 

 at once remove. If one of the whorls be submitted to the 

 microscope, it will be found to be composed, in part, of 

 slender filaments slightly beaded, and, in part, of other still 

 more slender threads, which are cylindrical, and from which 

 the first set of filaments would appear to arise, and both of 

 which are mixed together ; and again, if a portion of one of 

 the branches be examined from which the whorls have dis- 

 appeared, it will be seen to be composed almost entirely of the 

 exceedingly minute, and occasionally branched threads, with 

 here and there attached to them a single pyriform cell (see 

 fig. 3)., which is to be regarded either as the rudiment of the 



i 



