480 POLYMORPHISM AND LIFE-HISTORY IX THE DESMIDIACEiE, 



Var. HEXAGONUM(Elfv.)W. & G. S. West, forma major. 



(Pl.xiii.,f.3). 



Forma major, prse latitudine pauUo longior, Semicellulse 

 magis quadratse, lateribus longioribus; a vertice ellipticse mediis 

 lateribus angulatis, polls late-rotundatis. Long. 44; lat. 36;. 

 crass. 24/Li. 



Guildford. 



Compare Elfving, Desm. Finsk. T.i.,f.8j synonym Cos. Elfvingii 

 Rac, Desm. Polon., p. 27. 



Var. SAXONicuM(Rac.). (Pl.xiii., f.6). 



Long.44; lat. 40; isth.8/i. 



Canley Vale(llO). 



Syn. Cos. Elfvingii var. saxonicum Rac, Desm. Nowe, T.i., f.l4. 



This is practically var. Finmarkice with the basal angles- 

 developed into a tooth. Many other forms occasionally show the- 

 tooth, sometimes onl}' on one basal angle. The tooth is not per- 

 manent, but develops, as the cell grows, into the basal angle of 

 var. nodulatum. 



Var. AUSTRALE, n.var. (Pl.xiii., f. 15). 



Forma var. sa.xowico(Rac.) consimilis(sine dentibus); lateribus 

 brevibus, leviter divergentibus; angulis basalibus acuniinatis, 

 superioribus fere rectis plus minusve rotundatis; apicibus 

 arcuatis. Membrana minute punctato-scrobiculata, interdum 

 plicis subapicalibus binis, ternisve ornata. A vertice semi- 

 cellulse ellipticje polls rotundatis (vel aciiminatls 1) utrinque 

 inflatione glabra, bi-, tri-cuspidata vel bi-papillata instructie. 

 Long.38-42; lat.36-38; crass. 2 2-2. 5/x. 



Collector, Guildford(69). 



The above bears considerable resemblance to Cos. sulcatum 

 Nord.,(fornia) W. & G. S. West, Alg. Madag., PI. 9, f.28; and I 

 had, at first, the intention of making that the type-form under 

 the name of var. Madagascarense, However, the Madagascar 

 form is slightly flattened above, has more pointed angles, more 

 sloping sides below and the typical sulcatum end-view, in all of. 



