258 SEAWEEDS 



CHROOCOCCACE.E. 



General Characters. The Chroococcacecc are dis- 

 tinguished from the Nostocaccce not only by their 

 unicellular character, but more particularly by the 

 fact that they do not produce hormogonia, but uni- 

 cellular reproductive cells. Typically cell-division 

 does not occur in one direction only leading to the 

 formation of trichomes, but the direction varies with 

 more or less regularity, and since the daughter-cells 

 remain together in colonies within the original 

 envelope for a number of generations (Grl&ocapsa) 

 irregular gelatinous masses are thus formed. The 

 order is divided into two families, Chroococcccu 

 and CUamcesiphonecc, which may for convenience be 

 treated separately. 



The Chroococcece are best known by the genus 

 Glceocapsa. After each division of the mother-cell 

 the daughter-cells may be free to develop indepen- 

 dently, but usually they are held together by the 

 common gelatinous envelope for a succession of 

 generations. Spores are formed after the simul- 

 taneous change in habit of the whole colony of cells, 

 and in place of the gelatinous membrane a thick 

 membrane, rough on the outside, is developed. The 

 spore repeatedly divides, and soon forms in this way 

 a new normal colony of vegetative cells. 



The Chamcesiphonccc possess in Hyclla a genus of 

 perforating Algae, which at first sight appears to be 

 an approach to the Nostocacece, since the cells occur in 

 filaments. They are, however, so many individual 



