150 IIHODYMENIACE.E. v. 



As yet my only authority for claiming American Citizenship for tliis plant, is a 

 sino-le fragment picked up at Halifax. It is about an inch and half high, and three- 

 forked at half an inch from the base, the lobes linear, cuneate, dichotomous, spread- 

 ing ; the outline fan-shaped ; the ultimate lobes slender. One or two imperfectly 

 developed conceptacles are sessile on the ultimate laciniaj, about the middle. It is 

 to be hoped that some more fortunate collector may obtain satisfactory specimens. 



II. EUTHORA. J. Ag. 



Frond membranaceous, flat, dichotomo-pinnate, composed of two strata of cells ; 

 those of the inner stratum, oblong, large ; of the outer, coloured, minute, in few 

 rows. Conceptacles marginal, sub-spherical, with a closed cellular pericarp (com- 

 posed of concentrical layers of cellules at one point radiating) ; sporiferous filaments 

 very numerous, radiating from a central placenta, which is suspended in the cavity 

 of the pericarp by sub-simple filaments ; the fertile spore-threads forming roundish 

 masses of spores from their upper cells. Tetraspores cruciate, lodged in the 

 thickened apices of the frond. 



Separated from Bhodymenia, where it had been placed by Greville, by Professor 

 Agardh, on account of the different structure of the conceptacles, a character no 

 doubt of grave importance, although difficult to be seen without a careful dissection ; 

 and this is difficult to accomplish, owing to the minuteness of the object to be cut 

 through. In Rliodymenia the placenta projects from the base of the cell, and 

 throws up from its upper surface masses of spore-threads, which finally unite into 

 a. single globose nucleus ; in Enthora the placenta is in the centre of the cavity, 

 where it is suspended by cord-like filaments drawn from it to the surrounding 

 walls, and the spore threads issue from it on every side. This is the essential dis- 

 tinction. Another character is noticed by Prof. Agardh in the structure of 

 the walls of the pericarp, which in Euthora are composed of several sub-concentric 

 layers of cells, except at one spot, where the cells are set in lines radiating, like the 

 spokes of a wheel, from the nucleus outAvards, and indicating probably, as Prof. 

 Agardh suggests, the point where the wall first gives way to permit the escape of 

 the spores. 



1. Euthora cristata, J. Ag. ; frond fan-shaped, membranaceous, sub-dichotomous 

 or somewhat pinnately-multifid, the segments dilated upwards and repeatedly sub- 

 divided ; lesser divisions alternate, linear, laciniate at the ends, and often fimbriate 



