338 Mr. J. Ralfs on the Nostochinese. 



drospermum, by availing myself of the greater radiating capacity 

 of the former. 



The filaments, as in the other genera, have at first all their 

 joints uniform, but the terminal joint at each end soon enlarges 

 into a vesicular cell, which is either orbicular, elliptic or ovate, 

 and is generally furnished with fine scattered hairs or fibres : the 

 penultimate joints then elongate and become cylindrical, after- 

 wards they increase considerably in breadth, and when mature 

 are always elliptic or elliptic-oblong. Sometimes two or even 

 three sporangia are formed between the vesicular and the ordinary 

 cells. The additional sporangia however are not uniformly pre- 

 sent even in filaments from the same stratum, and are sometimes 

 double at one extremity and not at the other ; in fact, few mature 

 specimens can be examined without observing examples of these 

 variations. Hence, although the doubling of the sporangia oc- 

 curs more abundantly in some specimens or species than in others, 

 I cannot rely upon it as a specific distinction. 



There can be no difficulty in recognizing this genus under the 

 microscope. The filaments, especially when only one extremity 

 is visible, are remarkable for their animal-like appearance. The 

 chain of ordinary cells resembles a slender-jointed body; the 

 enlarged elliptic sporangium, at least twice as broad as the re- 

 mainder of the filament, represents the thorax, and the head is 

 mimicked by the vesicular cell, which, in colour, shape and ge- 

 neral aspect, differs from the other cells, whilst the presence of 

 fine hairs renders the imitation more perfect. 



It will thus be seen that the terminal cells are invariably vesi- 

 cular, the penultimate ones always become sporangia, and the 

 central ones remain unaltered. 



When the filaments break up, the sporangia separate from the 

 ordinary cells, but remain for some time crowned by the vesi- 

 cular ones. The filament in Spharozyga frequently breaks at the 

 vesicular cells, after which the portion retaining one attached to 

 its sporangium, appears, at first sight, to belong to this genus. 

 In the recent state however the slightest attention will show its 

 true character, for the vesicular cell of the broken Sphcerozyga 

 retains the punctum or globule at each end, which is not the 

 case in Cylindrospermum, as it is only present where another cell 

 has been conjoined. 



1. C. catenatum ( ). Filaments moniliform ; ordinary joints or- 

 bicular ; vesicular cells oval ; sporangia oval, catenate. 



This species was probably gathered in South Wales, but I 

 omitted to note the habitat when the specimens were preserved. 



Stratum bluish green ; filaments very fine, elongated, straight 

 or slightly flexuose, generally parallel. Ordinary cells orbicular, 



