JOUBNAL 



OF THE 



ROYAL IIOROSOOPIOAL SOCIETY. 



DECEMBER 1885. 



TKANSACTIONS OF THE SOCIETY. 



XYIII. — On some new and rare Desmids. 

 By W. Barwell Turner, F.K.M.S., F.C.S. 



{Bead 11th November, 1885.) 

 Plates XV. and XVI. 



The forms which I am herein describing are all more or less 

 beautiful, beauty being an especial attribute of this charming 

 family of micro-algse — so exquisite and curious are they that it is 

 a marvel that a larger number of observers do not take up their 

 study. The field is ample, and the life-histories of all but a very 

 small number are as yet unknown, the latter remark applying to 

 very common forms. 



In the following observations I have not taken the genera in 

 strict sequence, such sequence itself being a qusestio vexata. 



Genicularia De Bary. 



1. G. Americana nov. sp. Cells or joints comparatively short 

 and stout, covered with tiny granules spirally arranged in close 

 lines. Joints three and a half to six times as long as broad. 

 Chlorophyll radiate, but inclined to spiral form ; the moribund 

 and effete cell-contents (h) showing this inclination to spirals more 

 strongly ; two or more amylum corpuscles in each joint. Zygo- 

 spores not observed. iMinnesota, U.S.A. Fig. la, h, c. 



Cells, long. 71-5-143 ^i = -0028-56 in.; lat. 23-25-4 /z = 

 •0009- -001 in. 



This form differs considerably from the only species of the 

 genus hitherto described, G. spirotania Do Bary (' Conjugata),' 1 858, 

 t. iv. figs. 1-22), which is much longer and a little narrower in the 



Bcr. 2.— Vol. V. 3 1' 



