Protococcacece 



213 



Sub-family III. Sehma&trece. Cells elongated, ofteu greatly at- 

 tenuated and frequently curved; solitary or associated in definite or 

 loosely coherent colonies. One chloroplast in each cell. 



Sub-family IV. Oocystidece. Cells globose, ellipsoid, reniform or 

 sometimes sublimate. Daughter-cells generally retained in the en- 

 larged wall of the mother-cell. Several or many chloroplasts (rarely 

 one) in each cell. 



Sub-family V. Tctmedriece. Cells solitary ; flattened and angular, 

 with a definite number of angles, or tetrahedral, octahedral or poly- 

 hedral. Angles generally furnished with simple or furcate spines. 



Sub-family VI. Phytheliece. Cells globose or ellipsoid, solitary or 

 colonial, furnished with two or more long attenuated bristles. 



Sub-family VII. Dictyosp/Keriece. Cells globose, ellipsoid or ovoid, 

 associated to form colonies, and joined more or less completely by the 

 persistent old walls of the mother-cells, which sometimes become trans- 

 formed into special connecting-threads. 



Sub-family I. CCELASTRE^l. 



This is the only group of the Protococcaceae in which there is a 

 definite and regular coenobium of spherical or polyhedral form. 

 The cells are either globose or polygonal, with or without short 

 projecting processes, by means of which they are united to form a 

 hollow sphere ; or they are broadly lunate and united at the centre 

 of the spherical colony by short stalks. Multiplication is by the 

 formation of an autocolony in each cell of the coenobium, which is 

 ultimately set free by the dissolution or splitting of the mother- 

 cell-wall. 



Genus Coelastrum Nag., 1849. [Hariotina Dang., 1889.] The 

 coenobium, which is spherical or polyhedral, is hollow and is com- 



B 



Fig. 87. A, Coelastrum cambricuin Archer, from Lough Gartan, Donegal, Ireland. 

 B D, C. sphcericum Nag. ; B and C, small coenobia from near Penzance, 

 Cornwall; D, large cceuobia giving rise to daughter-coenobia (autocolonies), 

 from Bowuess, Westmoreland. (All x 475.) ' 



