A New Species of Gongrosira. 31 



non attenuatis, apicibus filamentorum e crusta calcarea protrusis ; 

 filamentorum erectorum cellulaj ut plurimum omnes ramorum 

 iaitia ostendunt. Cellulne plerumque subcylindricie, longitiidine 

 variabiles, diametro 1-9-plo longiores, omnes chromatophoro parie- 

 tali, pyrenoide singulo (rarissime binis) instructie. 



Zoogonidangia intercalaria, ore laterali prsedita, e cellulis 

 brevissimis fere semper oriunda. 



Crass, cell. fil. bas. 12-16 /i; crass, cell. fil. erect. 7 -5-9 '5 /a; 

 crass, zoogonidang. 16-19 /x. 



Hah. — Ad ^lignum vetustum in rivulis rapidissimum prope 

 Sidmouth, Devon. 



The thallus of Gongrosira scourfieldii may be roughly divided 

 into an upper part and a lower part, although there is no sharp 

 line of demarcation between these two layers. The lower part of 

 the thallus cannot be described as consisting of procumbent fila- 

 ments, since, although some of them are more or less creeping, they 

 form a loose anastomosis of short irregular branches. Springing 

 from this lower part of the thallus are numerous erect branches 

 which are themselves Ijranched. In fact, almost every cell of an 

 -erect branch exhibits a tendency to branch {vide fig. 1). The erect 

 branches are not attenuated, tlie apical cells being bluntly rounded, 

 and the tips of the branches project beyond the calcareous matrix. 

 The cells vary 'considerably in length, long cells and short cells 

 being indiscriminately mixed in the erect filaments. In the longer 

 cells, which are usually cylindrical and show no trace of incipient 

 branching, the parietal chloroplast is restricted to a part of the cell, 

 either submedian or terminal. Every cell of the thallus contains 

 a single parietal chloroplast with, as a general rule, one conspicuous 

 pyrenoid. Occasionally two pyrenoids are found in the chloroplast 

 {fig. 35), and very rarely there are chloroplasts without any 

 pyrenoids at all (fig. la). There are no empty cells — that is, cells 

 which have died and are in consequence devoid of contents — in 

 any parts of the filaments, either erect or procumbent. 



The zoogonidangia arise from short cells and are always inter- 

 calary with a rather wide lateral aperture (figs. 2 and 3 zg). 



There are two other incrusted species of the genus with which 

 {xongrosira scourfieldii should be compared, namely, G. trente- 

 pohliopsis Schmidle * and G. incriistans (Eeinsch) Schmidle.f From 

 the first-named G. scourfieldii is distinguished by its somewhat 

 larger size, its more irregular and on the whole more elongate cells, 

 its different branching, and its intercalary zoogonidangia. From 

 Cr. incrustans it differs in having less crowded erect filaments, which 

 are not parallel and are much more branched, and in the fact that 

 all the cells contain a large parietal chloroplast. 



* Schmidle in Oesterr. botan. Zeitschrift, 1897, No. 2. 

 t Schmidle in Ber. Deutsch. Bot. Ges., 1901, xix. p. 12. 



