THE MAKINE ALG.E OF NEW ENGLAND. 83 



Common on algoe and on sand- covered rocks at low water along the 

 whole coast. 



Not to be mistaken for any other alga on our coast. The gelatinous balls which 

 this species forms are found growing in large quantities at low-water mark, and are 

 sometimes called potatoes by the unromantic dwellers on the shore. 



Family CHORDARIE^E. 



Fronds cylindrical, branching, usually gelatinous, with an axis of 

 longitudinal filaments formed of long slender cells, and a cortex com- 

 posed of short, densely packed horizontal filaments formed of subspheri- 

 cal cells ; sporangia borne among the cortical filaments or formed directly 

 from them. 



Fronds tough and elastic, cortical filaments densely united to one an- 

 other . . Chordaria. 



Fronds gelatinous, cortical filaments only adhering loosely to one an- 

 other. 



Upper cells of the cortical filaments producing the plurilocular 



sporangia Castagnea. 



Upper cells of cortical filaments not producing sporangia. 



Mesogloia. 



CHOEDAEIA, Ag. 



(From chorda, a chord.) 



Fronds olive-brown, cartilaginous, filiform, branching; axial layer 

 composed of longitudinally elongated cylindrical cells and smaller wind- 

 ing cells packed closely together in a solid mass; peripheral layer 

 composed of short, simple, horizontal filaments, densely packed together; 

 unilocular sporangia oblong, borne at the base of the peripheral fila- 

 ments (paraphyses), plurilocular sporangia unknown. 



Tho distinction between the genera Chordaria and Mesogloia, in the absence of a 

 knowledge of the development of the fronds, must be quite arbitrary. In the present 

 instance we have considered that the genus Chordaria should be limited to the forms 

 having a tough cartilaginous substance and solid axis, of which we have only one 

 representative, C. flagelliformis. C. divaricata, both in its consistency and the devel- 

 opment of the frond, seems to belong to Mesogloia, accepting that genus in an 

 extended sense as we have done. 



C. flagelliformis, Ag. ; Phyc. Brit., PI. 3. PL V, Fig. 2. 



Fronds blackish, solitary or gregarious, attached by a disk, coriaceous, 

 lubricous, one to two feet long, filiform, solid, main axis usually undi- 

 vided, furnished with numerous long, subequal, flagelliform branches, 

 which are given off at wide angles, simple or with few, irregular, sec- 

 ondary branches; peripheral filaments (paraphyses) few-celled, cylin- 

 drical or slightly club-shaped; unilocular sporangia ovoid or pyriform. 



