spores within each cell of the colony. These become adjoined to 

 form daughter colonies before being liberated. There is but one 

 genus, Coelastrum, since "Phytomorula"^ has been found not to be 

 an alga. 



COELASTRUM Naegeh in Kuetzing 1849, p. 195 

 A hollow, spherical, free-floating colony of as many as 128 globose, 

 ovoid, or pyramidal cells which either are closely adjoined and 

 compressed, or interconnected by narrow processes to fonn a 

 fenestration. Daughter colonies are formed within the parent cells; 

 the walls of the parent cells may persist about the new colonies, 

 interconnecting them and so forming complexes. 



Key to the Species 



1. Cells without arms; interconnecting processes extremely 



short, sometimes scarcely evident 2 



1. Cells with arms, or with longer and very 



evident interconnecting processes 4 



2. Cell walls with wart-like processes C scabrum 



2. Cell walls without wart-like processes 3 



3. Cells spherical or ellipsoidal, closely adjoined, with interstices 



narrower than the diameter of the cells C. microporum 



3. Cells conical, adjoined, but with interstices as wade as the 



diameter of the cells, or wider - C sphaericum 



4. Cells pyramidal or conical; arms truncate, adjoined within the colony in 

 such a way as to form large fenestrations C proboscideum 



4. Cells spherical -_. 5 



5. Cells at the ends of long gelatinous strands 



radiating from a common center C. speciosum 



5. Cells not at the ends of long radiating strands 6 



6. Outer free walls of the cells with a truncate projection; 



interconnecting processes of cells short C. cambricum 



6. Outer free walls of cells without a projection; 



interconnecting processes long C. reticulatum 



Coelastrum cambricum Archer 1868, p. 65 

 PI. 53, Fig. 2 



Coenobium spherical, usually composed of 32 globose cells (rang- 

 ing from 8 to 128 in number), each cell adjoined to neighboring 

 cells by 6 broad, short projections of the sheath so that triangular 

 intercellular spaces result; outer free wall of the cells with a 

 flattened, truncate projection; cells 10-20/x in diameter, including 

 sheath. 



Widely distributed and common in the plankton of a great variety 

 of lakes and bogs. Mich., Wis. 



^Phytomorula regularis Kofoid, the only species described, has been shown to be pollen of 

 Acacia spp. (H. F. Copeland in Madroiio, 4, pp. 120-125. 1937); hence the family Coelas- 

 traceae is monogeneric, unless Chodat's genus Coelastrella should prove to be well founded. 



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