Tin: MAKINE ALG.T: of N1:W ENGLAND. 133 



PTILOTA, A jr. 

 (From rrrt/.uro^f feixtbercd.) 



Fronds com])resstMl, ancipital, decompound, ln-anclics distichous, jjcc- 

 tinatc-pinnatc, conii)osed of a inonosiphonous pinnate axis of larj;er 

 quadrate cells and a cortex of smaller cells; autlieridia terminal on 

 short corymbose branches; tetraspores tripartite; cystocarps (favellie) 

 terminal on the branches, usually invt)lucrate. 



An easily recognized j^enus, eoniprisin;^ abont twenty specit\s, of a deip red or red- 

 dish-brown color, only scantily represented on onr coast, bnt represented on the Cali- 

 foruian coast by a number of beautiful species. The genus reaches its greatest develop- 

 ment in Australia. The growth is by an apical cell, from which arises a monosi- 

 phonous axis of indefinite growth and short secondary branches. The origin of the 

 cortications has been fully explained by Na-geli in Die neueru Algensysteme, page 206. 

 The monosiphonous axis is clearly seen on holding specimens up to the light, and is 

 also visible at the growing tips where the cortications are wanting. The cortications 

 do not form a true solid tissue, but rather, as shown by Niegeli, densely interwoven 

 branching filaments. A detailed account of the development of the frond in dilTerent 

 epecies is given by Cramer in Physiologisch-systematische Untersuchuugen iiber die 

 Ceramiaceen. The development of the procarp is given by liornet in Notes Algolo- 

 giques, page 15. The position of the tetraspores is variable, and serves as a specific 

 mark. 



P. ELEGANS, Bonnem. (Ptiloia sericea, Ilarv., Phyc. Brit., PI. IDl.— 

 F.pJiimosa, var. tenuissima, Afr.) 



Fronds broYniish red, three to six inches bigli, main branches fili- 

 lorm. irre^irnlarly branching, secondary branches compressed, closely pin- 

 nate, with opposite pinnate branchlets, ultimate divisions without corti- 

 atiou; favellie terminal on the branches, irregularly lobed, naked or 

 with a short involucre ; tetraspores solitary on the ends of the branch- 

 lets, at first tripartite, becoming polysporic. 



On the under side of rocks between tide-marks and on shells and algre 

 in deep water. 



Throughout our whole limit ; Europe. 



A much more delicate species than the next, and recognized at once by the fact that 

 .0 younger i»arts of the branches are without cortications, whereas in the next species 

 the cortications extend nearly to the apex. It also dilfers in the position of the tetra- 

 spores, and the favella; are usually naked, while in the following species they arc sur- 

 rounded and almost concealed by a well-marked involucre. The usual color is a gray- 

 ish black, but in fading it often becomes pinkish. North of Cape Cod the species is 

 usually found clinging to the under surfaces of rocks at low-water mark, in company 

 with Ceramium IL}operi, lihodoihorton liothii, and Sphacelaria radicans. In such situa- 

 tions the specimens are small. At Newport and Gay Head the plant attains a much 

 larger size, and is abundantly washed ashore from deep water. 



P. SERRATA, Kiitz. 



Fronds dark red, three to six inches long, compressed, ancipital, de- 

 compound-pinnate, pinna? opposite, one pinna being short, undivided, 



