BY G. I. PLAYFAIR. 469 



Clilor. T.vi., f.44). Var. trnncatum is the form with which the 

 cell makes a new start in longitudinal growth. 



Var. CRENULATUM(Roy &. Bissett), non Ehr. (Pl.xi., f. 13). 



Forma Dog. traheculce, semicellulis apices versus attenuatis, rugis 

 14-16(visis 8-9) intra jiiarginera apicalem instructis. Long.520- 

 800; lat. bas.35-54; centr.32-51; ap.20-32^. 



Ubique (See slides 1,7, 10, 21 for fine specimens). 



Cf. Roy & Bissett, Jap. Desra., f.l9. I have never, however, 

 seen a specimen with a granulate apex. Here the apex is 

 invariably plicate within the margin. The younger cells are 

 attenuated from about the centre, but in more mature specimens 

 only near the tip. This attenuate tip, with its plicfe, is charac- 

 teristic of this form, which is the variation of trabecula commonly 

 found in this country. Lat. bas.42-45 is a general size for well- 

 grown specimens. Roy ct Bissett, I.e., identify this form with 

 Doc. crenulatum Ehr., but this seems doubtful, as Bailey (in 

 Ralfs, p. 2 19) identifies the latter with nodidosum. Doc. crenu- 

 latum Ehr., was an American form, and the figures in West(Frw. 

 Alg. W. Ire., PI. 19, f.8-12) show that the apex of nodidosum 

 {coronatum) may easily appear crenulate, or the undulations in. 

 tJlie sides might have given rise to the name; whereas in Roy & 

 Bissett's form the plications do not catch the eye even under a 

 ihigh majjuification. 



Var. MAXlMUM(Reinsch), forma. (Pl.xi., f. 15-1 6). 



Forma semicellulis apices versus paullo attenuatis; apicibus 

 trancatis, rugis 14-16(visis 8-9) instructis. Long. 730-875; lat 

 bas.44-58; centr.38-45; ap.28-30/i. 



Collector, Auburn(7, 10). Cum priori rarius. 



Doc. maxim,um Reinsch, is only the well-grown and strictly 

 -cylindrical form of trabecida, with a pronounced basal inflation. 

 Compare W. & G. S.West, Mouog., Pl.xxx., f.l2, 13, with Plxxxi., 

 f.l, 2, It is surely impossible to deny that these are the. same 

 plant in diti'ereut stages of growth. In this country, any speci- 

 jnen of trabecida over 400/m long is certain to have a plicate apex; 



