APR 1 8 2005 



GENERA OF PLANCTON ORGANISMS OF THE 

 CAYUGA LAKE BASIN. 



By O. a. Johannsen and J. T. IvLOVd. 



The more advanced student of Limnology will find at his disposal a 

 number of works for the identification of aquatic organisms. These books, 

 however, deal with limited groups, are not readih' accessible to the begin- 

 ning student and not adapted for class work, hence the following keys have 

 been prepared. To make the keys more generally useful some genera are 

 included which have not yet been recorded from this region, but which may 

 be found when our fauna and flora are better known. It will be noted also 

 that a number of forms, especially green algte, are included which are not 

 truly plancton organisms. The frequency with which they are brought in 

 from the smaller ponds and streams by students, makes this seem advisable. 



Except for the general arrangement, no originality is claimed for this 

 work. We are particularly indebted to the writings of Bessey, Birge, 

 Biitschli, Collin, Conn, Eyferth, Herrick, Hudson and Gosse, Jennings, 

 Kent, Stokes, Tilden, Van Douwe, West and Wolle. The figures are in 

 part drawn from the objects themselves, a few from photographs and some 

 from published papers. 



ALGiE.* 



a. Cells blue-green : reproduction by simple division. (See illustration I.) 



The blue-greens. (= Schizophyce.K) CYANOPHYCEiE. 



b. Cells unicellular or in clusters and colonies : not truly filamentous ; 



commonly embedded in a gelatinous matrix, more rarely free floating. 



COCCOGONE^. 

 c. Multiplication by vegetative cell division. Chroococcace^. 



d. Cells solitary, without gelatinous matrix, 

 e. Cells spherical. Chroococais. 



ee. Cells elongate. Cylindrical {Synechocoaus,' Chroothece') or fusi- 

 form ( Daclylococcopsis ) . 

 dd. Numerous cells in gelatinous matrix, 

 e. Colonies and gelatine without definite form, 

 f. Cells in several gelatinous capsules, 

 g. Cells spherical, enclosed in shapeless masses of gelatine. 



Gla'ocapsa. 

 gg. Cells elongate or elliptical. Ghrotheca, Zachariasia. 



fif . Cells scattered within the gelatinous mass, 

 g. Cell spherical (fig. 13). Aphauocapsa. 



gg. Cell elongate. Aphanothece. 



ee. Cells in definite arrangement. 

 f. Colonies free swimming, 

 g. Cell division in three planes, colonies therefore in clumps, 

 h. Cells spherical. 



♦Adapted from Conn, Engler-Prantl, Eyferth, et al. 



