118 NATURAL HISTORY SOCIETY OF DUBLIN. 



more or less immersed, pellucid orbicular nucleus with nucleolus (never 

 separate stellate chlorophyll bodies, as in Zygnema) ; the conjugation 

 takes place by short, wide processes (Figs. 2, 3), which circumstance, 

 along with the shortness of the cells or joints, gives the pair of conju- 

 gating filaments somewhat the appearance of a perforated ribbon-like 

 structure ; the total mass of cell-contents of each pair of conjugating 

 joints becomes combined with the other into an elliptic zygospore within 

 the inflated transverse tube; the longer diameter of the zygospore is placed 

 vertically to the length of the filaments ; the middle space occupied 

 thereby not becoming shut off from the cavities formed by the union of 

 the parent joints (Figs. 2, 3). 



That the total cell-contents, "primordial utricle" and all, wholly 

 coalesce to form the zygospore, I have completely satisfied myself, both 

 by there being no granular matter whatever left behind in the parent 

 conjugating joints, and by no further contraction of any contents taking 

 place on the application of reagents. In the same way it is equally 

 evident that the zygospore is not cut off from the cavities of the parent- 

 cells, but lies freely in the inflated transverse tube, though frequently 

 in contact with its walls about the middle. 



A seemingly fair figure of this type is given by Eabenhorst ;* but 

 the plant is referred by that author to Zygogonium in the Kiitzingian 

 sense, and de Bary's characters are not taken into consideration. Little 

 information can be drawn from the figure referred to as regards the 

 arrangement of the endochrome in the unconjugated joint; but it does 

 not seem either doubly-stellate or forming a compressed band, but scat- 

 tered. If the former, it would be a Zygnema, with the zygospore in 

 the middle. It might possibly be assumed, indeed, that the figure may 

 represent the broad or flat view of the band of endochrome as towards 

 the observer. Therefore Rabenhorst's figure would be still more likely 

 to represent a plant congeneric with the present, seeing that here the 

 whole cell-contents are represented as fused into the spore, no part 

 of the whole united mass of contents being shut off from the spore 

 itself, but the cavity being empty, with the exception, of course, of the 

 centre of the transverse tube occupied by the spore ; but I hardly think 

 his plant specifically alike, owing to the endochrome therein not form- 

 ing a compressed axile band. 



JSTow, the foregoing characters of the plant, here drawn attention to, 

 as has been described, would seem at once so decisive, that it should be 

 referred to Mougeotia (de Bary, non Agardh), and not to Zygogonium 

 in either sense, that it might almost be asked why there should be any 

 question on the subject, or any allusion to the genus Zygogonium (de 

 Bary), or Zygogonium (Kiitz.), as connected with it. The reason for 

 this I shall presently advert to. 



Having thus reached the genus to which I am disposed to believe 

 our plant truly belongs, it is perhaps well that I should here try to 



* " Kryptogamen-Flora von Sachsen," &c, p. 162. 



