171 HVDRO1DA. HALE. 



Genus PLUMULARIA, Lamarck (in part). 

 PLUMULARIA ZYGOCLAUIA, .s/>. nov. 

 (Plate xxxvi., fig. 2.) 



Hjdrophyton about one and a half inches in height, very 

 slender, rarely branched, monosi phonic, divided into long inter- 

 nodes, each of which bears a hydrotheca and a pair of hydrocladia 

 at the lower extremity. Hydrocladia opposite, internodes long, 

 each (except the proximal one) bearing a hydrotheca ; nodes 

 very oblique. Isolated secondary hydrocladia occasionally 

 present. 



Hydrotheca? borne at the lower ends of the internodes, at an 

 angle of about 40 ; campanulate, border circular, entire, back 

 free. 



Sarcothecae bithalamic, canaliculate, short, stout, rigid, 

 widest in the middle of the terminal loculus ; one at each side of 

 the hydrotheca, one in front, one on the upper part of the 

 hydrothecal interuode, one on the proximal internode of each 

 hydrocladium, and several in line on the front of each stem- 

 in ternode. 



Goiiotheca? : female, pear-shaped, slightly flattened above, 

 opercnlate, with a sub-globular segment between the pedicle and 

 the capsule itself, a sarcotheca on each side near the base : 

 (male, smaller, ovate, not flattened above, with a single 

 sarcotheca only ?) 



Colour. Whitish. 



This very delicate little species is almost a replica of the 

 slenderest forms of P. campanula, except in the ramification, 

 the hydrocladia being paired and opposite instead of alternate. 

 P. campanula varies greatly in regard to the length of the 

 hydrothecal internodes, and the consequent distance apart of 

 the hydrotheca^ ; whether the present form is similarly variable 

 remains to be ascertained, but the few specimens found all have 

 long slender internodes. As in the allied forms there is a 

 tendency for the hydrothecal internodes to be divided by a more 

 or less distinct joint above the hydrotheca, so as to form inter- 

 mediate interiiodes. While the hydrocladia are in very regular 

 opposite pairs, the secondary hydrocladia which are sometimes 

 produced are given off singly and irregularly. I found a true 

 branch only in one case, which took the. place of a hydrocladium. 



Not only are the mesial sarcotheca rigidly fixed, as in most of 

 our Plumularice, but the snpracalycine pair also are too stout at 

 the point of origin to admit of their free movement. Their 



