XV111 FRESH-WATER ALG^ OF THE UNITED STATES. 



attention. It is found on old walls, damp mossy earth, old wood, 

 and is not infrequent in green-houses. The plant in younger 

 and older conditions was found to represent the following forms : 

 first, Lyngbya f onus, viz., Lyngbya foveolarum Mont., [Oscillaria 

 (Leptothrix) foveolarum, Eab. ;] L. Calcicola (Kg.) Hansg. [Lep- 

 tothrix calcicola Kg., Hypeothrix calcicola Eab.] Oscillaria 

 Kuetzingiana Nseg. ; Oscillaria tennis Ag. ; Lyngbya vulgaris 

 (Kg.) Kirch., (Phorinid. yulgare, Kg.) Lyngbya antliaria (Jurg.) 

 Hansg.; Symploca niuralis Kg., Symploca melanocephala Kg., 

 Microcoleus terrestris Desm. Stigonema-forms ; Stigoneina Bou- 

 teilli (Breb. et Desm.) Hansg. (Sirosiphon Bouteilli Breb. et 

 Desm.) Nostoc-forms ; Kostoc Sphseroides Kg., N". gelatinosum 

 Schon., including N". Delphinii, Bor. Unicellular -f oy^ms ; Chroo- 

 coccus minor Naeg. Chr. pallidus Naeg. Chr. aurantio-fuscus 

 (Kg.) Eab., Gloeocapsa seruginosa Kg., Gl. didyma Kg., Gl. 

 quaternata (Breb.) Kg., Gl. sanguinea Kg., Aphanocapsa cruenta 

 (Ag.,) Hansg. [Porphoridium cruentum (Ag.) 2s"aeg.] 



Some pages are devoted to an account of the development of 

 Ulothrix flaccida Kg. The following are forms or conditions 

 through which this plant passes. It is made to include U. 

 nitens Menegh., Conferva antliaria Kg., Psichohorinium antli- 

 arium Kg., Gloeotila ealdaria Kg., and embraces the following 

 unicellular forms, viz., Stichococcus bacillaris 2s"aeg., Dactylo- 

 coccus caudatus, Hansg., D. bicaudatus A. Br., Dactylothece 

 Braunii Lagh., Protococcus viridis Ag., Chlorococcum humi- 

 cola Eab., Cystococcus huniicola Naeg., Pleurococcus vulgaris 

 (Grev.) Menegh., PI. pulcher Kirch., PL miniatus (Kg.) K"aeg., 

 PI. aureo-viridis (Kg.) Eab., Protococcus grumosus Eich., P. 

 cinnamoneus (Menegh.) Kg., Gloeocystis fenestralis (Kg.) A. Br., 

 (Gloeocapsa fenestralis) Gl. vesiculosa Naeg., Palmella hetero- 

 spora, Eab. ? and P. botryoides Kg. 



These two plants are quoted, the one a Cyanophycece and the 

 other a Chlorophycece as instances of the multiform transfor- 

 mations to be observed in the development of Fresh-water Alga3. 

 Many others might be cited from personal observation as well as 

 from the notes of Dr. Hansgirg and others, all demonstrating 

 the position assumed, and often referred to in the body of this 

 work, that the algee forms undergo many polymorphic changes 

 before they come to a full development. 



It is evident that sooner or later the whole system of classifi- 

 cation must be changed. The present system is altogether too 

 artificial, separating as it does many forms not only into different 

 genera, but into different families, and orders, which are geneti- 

 cally connected. Our present knowledge is too imperfect for a 



