Mr. J. Rolfs on the Nostochinese. .327 



Trichormus, Allman. 



Filaments simple, moniliform, distinctly jointed, aggregated into 

 an indeterminate gelatinous stratum ; sporangia separated from 

 the vesicular cells by the ordinary joints, which they more or 

 less resemble in form. 



(Anabaina, Bory, Brebisson, Kutzing, Montagne and others.) 



In Trichormus the stratum is indeterminate and very gela- 

 tinous ; at first it is nearly colourless and transparent, and the 

 filaments are only sparingly scattered through the matrix ; but 

 the filaments rapidly increase in number, and the mass, gra- 

 dually becoming more opake, acquires at length a deep bluish 

 green colour, which is occasionally mottled with brown, especially 

 beneath. 



The filaments are mostly short, distinctly moniliform, and fre- 

 quently as much curved as those of a Nostoc. The cells are all 

 more or less orbicular, and the sporangia differ less from the 

 ordinary cells than they do in the following genera. Viewed 

 under the microscope the filaments scarcely differ from those of 

 a Nostoc. In both genera they are usually curled, their cells are 

 orbicular, the vesicular ones are interstitial and terminal, and the 

 sporangia are often not apparent, or are known only by their 

 denser endochromes. 



In some of the aquatic species the stratum separates into large 

 floating gelatinous masses, and then can only be distinguished 

 from Nostoc by the gelatinous portions having no definite form 

 or size, and by the absence of an epidermis. 



Professor Kutzing refers Monormia intricata, Berk., to this 

 genus. I have never gathered that plant, and I was unable to 

 determine the genus from recent specimens sent me by Mr. 

 Thwaites from Bristol; but, judging from Mr. Berkeley's figures 

 and description, I should suppose that the more definite frond 

 and the elongated, solitary and peculiarly convoluted filament 

 are sufficient to sustain the genus. 



As Professor Harvey has reminded us in his f Phycologia Bri- 

 tannica ' that Bory's name Anabaina has been appropriated to a 

 genus of flowering plants, and it becomes necessary to choose 

 another, \ have adopted Professor Allman's name Trichormus as 

 next in priority. 



Trichormus differs from Dolichospermum in its sporangia, which 

 are more or less orbicular, and from Spharozyga and Cylindro- 

 spermum by the different arrangement of the sporangia and vesi- 

 cular cells. 



1. T. Flos-aquce (Lyngbye). Filaments flexuose or curved, monili- 

 form ; cells orbicular, vesicular ones larger, terminal and interstitial. 

 Nostoc Flos-aquce, Lyngbye, Tentamen Hydrophytologiae Danicte, 



