166 CONJUGATEJi. 



our knowledge of the AlgcB has been so considerably aug- 

 mented." — Annals, 



12. MESOCAEPUS Hassall 



Char. Cells JiUed at first loith endochrome, ivhich subsequently 

 contracts, and assujnes an irregularly spiral form. 

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

 verse tubes. 



Derivation. From fiscros, middle, and Kaprros, fruit. 



Sph<Brocarpus Hassall, in Annals of Nat. Hist. vol. xi. 

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



The genus Mesocarpus, for which I first proposed the name 

 of SphcBrocarpus, to designate the position of the sporangia, 

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

 two genera already described in not having the endochrome 

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

 ments are 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- 

 daridecB, 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 scalaeis Hass. 



Plate XLII. Fig. 1. 



Char. Filaments exceeding someiohat in diameter those of 

 Mougeotia genufiexa. Cells about four times as long as 

 broad. Sporangia oval, their long diameter being placed in 

 the direction of the diameter of the cells. 



