150 Kansas Academy of Science. 



Family II. Chroococcace^. 



Key to the Genera of Chroococcaceas. 



Plants solitary or associated in families or colonies, surrounded by a 

 common gelatinous tegument. 



A. Colonies without definite shape, individual sheaths thick, remain- 

 ing through many divisions, sheath of original mother cell sur- 

 rounding entire colony; cells spherical enclosed in sheath single 

 or in colonies; cell contents blue-green 1. Gleocapsa. 



B. Colonies having a definite characteristic shape, free-floating. 



* Cells spherical, having an indefinite arrangement, forming 

 several layers; colonies of variable shape, at first solid, be- 

 coming saccate and clathrate 2. Clathrocystis. 



* * Cells spherical having a definite rectangular arrangement, 

 forming a single layer 3. Merismopedium. 



1. Gleocapsa. 



1. G. arevaria (Hassall) Rabenhorst. Plate II, fig. 1. 

 Kansas: Paola, July, 1916. 



Iowa (4). 



2. Clathrocystis. 



2. C. seruginosa (Kuetzing) Henfrey. 



Kansas: Emporia, found in large amounts in August 

 and November, 1915; March and August, 1916; 

 Osawatomie, November, 1915; April, 1916; Burling- 

 ton, April, 1916; Coffeyville, July, 1916. 



Iowa (4); Missouri (11). 



3. Merismopedium. 



Keii to ftpecies. 



Diameter of cells, 3-6 mic, colonies, 45-150 mic. in di- 

 ameter M. glaucum. 



Diameter of cells, 1-3.2 mic M. tenuissimum. 



3. M. glancum (Ehrenberg) Ndgeli. Plate II, fig. 2. 

 Kansas: Garnett, August, 1916; Lyndon, March, 1916; 



Osawatomie, August and November, 1916; Coffey- 

 ville, October, 1916. 



Iowa (4); Nebraska (24); Colorado (15). 

 i. M. tenuissimum Lemmermann. 



Kansas: Burlingame, October, 1916. 



Colorado (15); Missouri (11). 



Order II. HORMOGONE^. 

 Key to Families of Hormogonese. 



I. Filaments frequently branched, containing one or more trichomes; 

 sheaths variable, more or less gelatinous; trichomes consisting of a 

 simple row of cells uniform along their entire length, except for the 

 apical cells which are sometimes attenuated; heterocysts absent; 

 reproduction by vegetative division Oscillatoriacese. 



II. Sheaths very delicate, often invisible ; trichomes usually tortuous and 

 entangled, consisting of a single row of uniform cells, with hetero- 

 cysts; reproduction by means of vegetative division, hormogones and 

 gonidia Nostocacese. 



