86 ARCHER AND DIXOX, ON' DESMIDIACE.E. 



(fig. 9), a fair idea of which in the normal state can be 

 obtained by imagining the irregular central growth as absent, 

 and the two older segments in apposition. It will be seen 

 that this variety agrees with Micrasterias Jenneri, Ralfs, 

 variety ft, in the superficial granules being somewhat large, 

 giving a somewhat dentate or roughish appearance to the 

 margin, but it differs from both varieties, a and p, by its 

 lateral lobes not being bipartite, and of course wanting their 

 emarginate subdivisions. Thus, if Mr. Ralfs justly called 

 this species, both a and ft, puzzling, the drawing before us 

 exhibits a form even more so (vide ' British Desmidiese/ p. 

 76). On account of the lobes not being incised, as just 

 pointed out, this form (of course I need not repeat that I 

 do not allude now to its abnormal irregularity) becomes, I 

 think, likely to be mistaken for an Euastrum, to which genus 

 it closely approaches through E. oblongum. INT or is the 

 resemblance lessened by there occurring occasionally speci- 

 mens with the incisions between the segments, not linear, and, 

 therefore, the lobes not closely approximate, but spreading 

 and sinuously lobed. However, the absence of any infla- 

 tions, when viewed laterally, as well as the want of a 

 terminal linear notch, though there is a slight concavity or 

 depression at the ends, whilst the lobes arc cuneate and more 

 radiant, exclude this form from Euastrum. I would here 

 then, take the opportunity to characterize this plant thus ■ — 



Micrasterias Jenneri, Ralfs, var. y. 



Granules giving a rather rough appearance to the margin, 

 lateral lobes concave, not bipartite, without emarginate sub- 

 divisions. 



Locality : Bog, near Carrickmorc, county of Tyrone. 

 This very interesting variety occurred in the gathering kindly 

 forwarded to me by the Rev. R. V. Dixon, and which also 

 contained his new form, Tetrachastrum mucronatum. 



In the monstrosity of Staurastrum defectum, as shown in 

 the drawing (fig. 10), we have both the new segments well 

 developed, and each possessing in the front view its own 

 proper laterally projecting spines; but the interposed seg- 

 ments remain confluent throughout ;i portion of their ter- 

 minal margins, forming a bluntly triangular notch at the 

 sides, the whole making but one entire cavity, with the 

 endochromc loosely scattered within. In the next ease, that 

 of Artlinxh'smiis ///ens (fig. 11), the resulting fusion of the 



new growth, which ought to have formed two new segments, 

 is even greater than in the preceding instance, so that the 



