166 CONJUGATED. 



our knowledge of the Alga has been so considerably aug- 

 mented." Annals. 



12. MESOCARPUS Hassall. 



Char. Cells filled at first with endochrome, which subsequently 

 contracts, and assumes an irregularly spiral form. 

 Sporangia either circular or oval, and lodged in the trans- 

 verse tubes. 



Derivation. From pscros, middle, and Kapjros, fruit. 

 Sphcerocarpus Hassall, in Annals of Nat. Hist. vol. xi. 

 p. 185. pi. 7. fig. 7. &c. 



The genus Mcsocarpus, for which I first proposed the name 

 of Sphcerocarpus, to designate the position of the sporangia, 

 and which I now find to be preoccupied, differs from the 

 two genera already described in not having the endochrome 

 arranged in any definite and figured form. When the fila- 

 ments arc young, the endochrome occupies the entire cavity 

 of each cell ; as they grow older, however, spaces are left at 

 the extremities of the cells; and finally the endochrome 

 frequently contracts itself into a mere thread, irregularly 

 twisted. The sporangia are never placed in the cells, as in 

 all the species of the genus Zygnema, and in very many Tyn- 

 daridece, but invariably in the transverse tubes of commu- 

 nication which become dilated for their accommodation. The 

 species of this genus live in water, less pure than the Zygne- 

 mata and Tyndaridece, being mostly found in boggy and 

 ancient ponds, on commons, &c. ; and on this account they 

 are rarely so brightly coloured as are the species of those 

 genera. 



1. MESOCARPUS SCALARIS Hass. 

 Plate XLII. Fig. 1. 



Char. Filaments exceeding someivhat in diameter those of 

 Mougeotia gemiflexa. Cells about four times as long as 

 broad. Sporangia ova I, their long diameter being placed in 

 the direction of the diameter of the cells. 



