Marine Algce of Benvick-on-Ttveed. 311 



parenchymatous throughout, the cells of the thallus a little 

 broader than long. The fructification is in external convex warts 

 (nemathecia), the tetraspores cruciate, large, almost as long as 

 the nemathecial filaments, the cj^stocarps composed of few spores 

 placed one above the other, in one, two, or three rows. The 

 nemathecial filaments are short and composed of few cells, which 

 are twice as long as broad below, much shorter above. 



Peyssonnelia Harveyana, Cm. 

 in J. Ag., Spec. Alg. n., p. 501. 



Descr. Peyssonnelia Harveyana, J. Ag., I.e. 



Fig. „ „ " Cm., Fl. dn Finist., pi. 19, Gen. 129, 



figs. 4 and 5. 



ffab. On rocks near low-water mark. Fruit Winter. Rare. Berwick 

 Bay. 



The fronds of the present species are thicker and smoother 

 than those of P. Dubyi, which outwardly they much resemble. 

 Under the microscope, however, the two species are easily 

 separable. The fronds of P. Dubyi are very thin, and composed of 

 large cells which are broader than long in all parts of the frond. 

 In specimens bearing favellse the cells of those portions of the 

 frond underlying the nemathecia are much smaller just below 

 the nemathecial filaments than at the base of the frond, but they 

 are still broader than long or, square. In P. Harveyana the 

 fronds are thick and composed below of large angular, irregularly 

 shaped cells, which become gradually narrower upwards till 

 near the surface of the frond they are not much more than half 

 the breadth of the basal cells. The cells are usually about tivice 

 as long as broad, except near the centre of the frond where a few 

 rows of nearly square cells occur. 



With us P. Harveyana is very much rarer than P. Dubyi. 



RHODODERMIS, Crouan. 



Rhododermis elegans, Crouan. 



in J. G. Ag., Spec. Alg., p. 505. 

 Descr. Bhododermis elegans, Crouan, I.e. 

 Fig. „ „ Crouan, Flor. du Finist., pi. 19, fig. 130 



(upper figure). 

 Syn. „ „ J. G. Ag., Epicr., p. 391. 





