178 FRESH-WATER ALG^E OF THE UNITED STATES. 



CHARACITJM NAEGELII, A. Br. 



Cells elliptical or inverted egg-form when fully developed, 

 2-3 times longer than broad, always with rounded apex, 

 stipe short, not dilated at the base. Cytioplasm bright 

 green, granular. 



Diameter of cells, 7-18 ^. 



This form approaches very nearly to C. Sieboldi, also of 

 A. Br. Can scarcely be separated except by size. Thus 

 governed, it is C. Naegelii. 



Ponds, not frequent. 



Plate CLIX, fig. 4, filament of Oedogonium full of the 

 plants ; two of them more fully matured than the rest. 



CHARACIUM HETEROMORPHUM, Eeinsch. 



Cells at first globose-elliptical, attenuated below into a 

 thin hyaline stem ; contents granular, then contracted in 

 preparation for formation of the gonidia ; zoogouidia elon- 

 gated, escaping at the broadly opened apex. 



Diameter of cells, 8-10 p ; 2-3 times as long as broad. 



&y \\.Hydrianum heteromorphum, Rab. 



The distinction between the present genus and Hydrl- 

 anum, Bab., being somewhat uncertain in the progress of 

 development, I have followed the example of Dr. Kirch - 

 ner by uniting the two. C. heteromorphwn would be a de- 

 cided Hydrwnum, but the first three on the list, C. sessile, 

 C. acutum and C. Pringsheimii would hold a more question- 

 able position between the two genera. 



Genus 49, PROTOCOCCUS, Ag. 



Spherical forms not attached, not branched, in the strictest 

 sense unicellular, single or gathered into irregular clusters, 

 primarily always filled with chlorophyl green cytioplasm, often 

 changes to red by exposure and other circumstances. 



They multiply rapidly by the process of cell division. 



As plants they have no value in the system of classification. 

 More modern observations show that, as a rule, they are merely 

 an intermediate condition of growth of higher filamentous 

 plants. Have included under this head also the old genus of 

 Chlorococcum and Pleurococcum, thus embracing a heterogeneous 

 variety, all with hyaline cytioderm, mostly without tegument, 

 swimming free, forming a scum on stagnant waters ; or out of 

 the water, on trunks of trees, old wood, moist or shaded rocks, 



