760 Proceedings of the Royal Irish Academe/. 



A long and careful examination of the ISew Zealand specimens 

 has found no sporangia carried above the disc ; but sterile hairs, like 

 those described and figured by Mobius, are present as a rule in great 

 numbers, though in some cases entirely absent. 



The form of the thallus is in marked contrast to the broad- 

 spreading, smooth-edged plates of Phycopeltis expansa. In all cases 

 it consists of radiating branching bands, spreading from a centre. 



The margin of the lobes is usually clear and defined, but 

 occasionally the thallus breaks into a network of filaments. This, 

 however, only happens rarely on a very small scale, and seems to 

 be an accident, due to some interference with the normal growth, 

 rather than a distinct habit of the species. 



Examination with a lens shows that some plants present a dull 

 opaque black surface, others a brighter appearance. This difference 

 is due to the absence of hairs in the former case, and the minute size 

 of the cells. 



The cells are normally of rectangular form, but in parts, where 

 the thallus assumes the reticulate mode of growth, they tend to 

 become rounded and form more or less moniliform rows. In other 

 parts the cells become irregular and sinuous, as described by Mobius, 

 though there is no apparent cause for this curious effect. 



In. size also there is considerable variation, as in the specimens 

 described by Mobius, and the varieties with different forms of cells, 

 may grow adjacent to one another. 



The type-form has cells which may reach a diameter of '01 mm., 

 and possesses numerous barren hairs. In the atrichous varieties the 

 cells are commonly less than a quarter as large. 



The hairs are about '15 mm. long and consist of 10 to 20 cells. At 

 the base they are slightly narrowed and rise from a dome-like eleva- 

 tion of one of the disc cells. The free end terminates in an ob- 

 tuse or sub-acute cell which sometimes bears a minute hyaline knob 

 such as is commonly seen in certain species of Trentepohlia, as T. 

 iolithus for instance. 



Branching never occurs ; nor is there any trace of the forma- 

 tion of terminal or lateral outgrowths of the nature of spores or 

 sporangia. 



