300 THE AMERICAN MONTHLY [Oct., 



1-7353 in. broad. It has been called Raphidium fascicula- 

 tiim by F. T. Kutzing, in liis "Species algarum," 1849. 

 He gives the synonyms of this form thus : Binatella 

 calcitrapa, A. de B. Alg. Fal. PI. VIII. ; Closterium gre- 

 garium Menegh. ; Xanthidium (?) difforme C. Gr. E. Infus. 

 p. 147, Tab. X, Fig. XXVI. ; Staurastrum falcatum et 

 paradoxum Ehrenb. ; Ankistrodesmus falcatus A. de B. 

 in list, 1845 ; Micrasterius falcata Corda, and Closterium 

 falcatum Menegh. 



It is like a Closterium, being elongated and attenuated 

 but aggregated into families forming fascicule or faggot- 

 like bundles. This is the way they appear commonly, 

 but mine are single. Then there is a form, called An- 

 kistrodesmus convolutus Corda, in which the cells are 

 much curved, cresent shaped, somewhat rapidly atten- 

 uated with the ends subacute. But A. falcatus passes 

 into that by imperceptable degrees. There is another 

 form called A. contortus in which the cells are arcuate 

 or sigmoid, somewhat gently inflated at the centre and 

 the ends are drawn out long and very fine. Now these 

 three forms, or species as they are called, can hardly be 

 distinguished. Which can we say are arcuate or sig- 

 moid, slender or not attenuated ? In my form, I see the 

 passage from one into the other and they are not aggre- 

 gated into faggot-like bundles but separate and swim- 

 ming about in the water, very slowly it is true. So I 

 shall make it into the form, for I am indisposed to call 

 them species of falcatus. And as to the genus Ankistro- 

 desmus, I cannot see how the growing in faggot-like 

 bundles is distinctive for they do not so grow. They 

 must be placed in Closterium P. A. C. Nitzsch. But the 

 genus of these forms I do not now wish to go into. I 

 merely wish to place the form in the genus Closterium 

 falcatus A. de B. and described as above. I call attention 

 to these beautiful atomies, the Desmids, so as to show 

 t,hat they will warrant study. 



