Mr. HassalFs Notices of British Freshwater Alga. 185 



a deep piu'plc. It is (listinguislied from ^t. glutinosns by the form 

 of the sporangmm, size and colour of the filaments *. 



St. virescens. For description see 'Annals and Magazine of 

 Natural Histoiy/ vol. xi. ; and for figm-e, PI. VII. and tig. 3. 



SynonjTn, Mougeotia quadrangulata, ' Annals and Magazine of 

 Natm"al History/ vol. xi. 



This is readily distinguished from the two preceding species by 

 its much smaller size. 

 St. . Filaments usually of a green colour and smaller 



diameter than those of St. affinis ; cells before conjugation 



about eight or ten times as long as broad, but after that period 



becoming much longer ; sporangium cruciform. PI. VII. fig. 4. 



Hab. Pond near Roydon, Essex. 



This species comes very near to St. virescens, from which it is 

 distinguished by its somewhat finer filaments and cruciform spo- 

 rangium, the sporangium in St. virescens being square. 

 St. gracilis. Filaments of finer diameter than those of St. affinis, 



and usually of a green colom* ; cells many times longer than 



broad; sporangia cruciform. See fig. 5. 



Hab. Penzance, Mr. Ralfs ; Rackham Bogs, Broadwater Forest, 

 Fishers Castle, Parham Park, ]\Ir. Jenner ; High Beech, Hertford 

 Heath, Wormly West End, and Wanstead Flats, Essex. 



This is an abundant species, and very distinct from any of the 

 others. It was found by 5lr. Kalfs, Mr. Jenner and myself, within 

 a few days of each other. 



St.gracillimus. Filaments more slender than those of St. gracilis, 



and usually of a green colour ; cells very many times as long 



as broad ; sporangia cruciform, and about one-half the size of 



St. gracilis. See fig. 6. 



Hab. Hertford Heath and High Beech, A. H.; RackhamBogs 

 and Parham Park, Mr. Jenner. 



This species I have myself met with several times, but did not 

 at first recognise its distinctness, of which however I now enter- 

 tain no doubt ; and it was only on the receipt of a beautiful sketch 

 from Mr. Jenner, accompanied by remarks, that I examined 

 thoroughly into the matter and satisfied myseK of its entire di- 

 stinctness. 



Nov. gen. Sph.erocarpus. 

 Cells filled at fii'st with endochrome, which subsequently contracts 



and assumes an irregularly spiral form ; sporangia cu'cular, 



lodged in the transverse tubes. 



* I have since ascertained that this species was first descvibcd in the 

 ' English Botany.' I have, however, retained Agardh's name for it, the 

 term ccerulescens being rarely, if ever, applicable to it, and therefore likely 

 to mislead. 



Ann. ^ Mag. N. Hist, Fo/. xii. O 



