('YUNDUnCYSTIS. 



with a slight median constriction, apices rounded ; each 

 chloroplast with a prominent pyrenoid. 



Zygospore unknown. 



Length 10'5-13|u; breadth o'o-7,. 



IE-ELAND. Lough Xeagh ! ; along the shores. 



Geoyr. Distribution. India. Ceylon. 



We think this plant is correctly placed in the genus Ci/lin- 

 ilrnri/x/ix, and it is much the smallest known species. The 

 Irish specimens were a little- smaller than those observed from 

 India, but otherwise were very similar. 



Genus (.). NETRIUM (Xiig. 1849). 



Nag. G;itt. eiuz. Ali;-. 1X1!), p. 107 (subgeuus of Clo-itcrium). 



Itzin'.s. tt liuthu, in llubenh. Alg. ISolj, no. 508 (genus without description) . 



Liitkem. Zellmembr. Desmid. 1902, p. 395, 396, 407. 



Cells straight, cylindrical, subcylindrical, or fusi- 

 form, without any median constriction ; cell-wall un- 

 segmented, without pores, destitute of a differentiated 

 outer layer and quite smooth ; chloroplasts two (in one 

 species four), one (in one species two) in each semicell, 

 each chloroplast axile with about six radiating longi- 

 tudinal plates which are conspicuously notched at their 

 free edges (in all except N. interruptum) ; pyrenoids 

 several in each chloroplast, arranged in a median 

 series or sometimes scattered. 



The establishment of this genus was suggested by Liitke- 

 muller in order to include four forms which obviously do not 

 belong to the Placoderm Desmids. The present genus Peniiiin 

 is the most artificial of the genera of Desmids,, containing in 

 addition to its true members quite a number of widely different 

 forms, some of which really belong to the Cosmariea3, others 

 to the Closteriese, and those now included in the genus Natrium 

 which belong to the Spirotasnieae. 



The species included under the generic name Netrini/t, have 

 long been considered as forms of l\'.niuin, but the structure of 

 the cell-wall the absence of segmentation and of the differ- 

 entiated outer layer places these plants at once- in the tribe 

 Spirotgenieae. 



The chloroplasts are axile and are furnished with a number 



