472 POLYMORPHISM AND LIFE-HISTORY IN THE DESMIDIACE^ 



sursum interdnm inflationibus minoribas, ad apices versus leviter 

 attenuatae; apicibus truncatis, rugis 14-16 (visis 8-9), vel sjepe 

 granulis 12-16 (visis 7-9), vel granulis 6 (visis 4) infra marginena 

 ornatis. Sutura prosiliente. Membrana vulgo dilute scrobiculata. 

 Long.390-500; lat. bas.30-39; centr.28-35; ap.20-27/i. 



Auburn(7, 10, 16, 21), Coogee(l, 4), Guildford(78, 114). 



Wherever well-grown specimens of Doc. trabecula var. crenu- 

 latum are met with, the above form is sure to be found accom- 

 panying them, along with some form of var. Ehrenhergii. In 

 slide 1a(N.H.S.) mounted haphazard from a pure gelatinous 

 crust of Desmids obtained at Coogee, there may be seen, side by 

 side, four forms exhibiting plainly the development from var. 

 Ehretibergii to var. crenulaiuui. (I) Var. Ehrenbergii, lat. bas. 

 20/Li(Pl.xi , f. 10). (2) Var. constricticin mihi, lat. bas.28/x(Pl.xi., 

 f.U). (3) Var. Z)e^;)o?i«eimihi, lat.bas.34^(Pl.xi.,f.l2). (4) Var. 

 crenulatum, lat. bas.42yLi(Pl.xi., f. 13). The forms of var. Delponiei 

 seem to have a strongly granulate apex more commonly than any 

 other form in this species. Pl.xi., t.17-21 show five varieties of 

 apex found in specimens of this variety. ( Ftc^e note on this varia- 

 tion, supra). 



Forma mediol^vis (Playf.). PL mediokeve, ante, 1907, 

 Pl.ii., f.lO. 



Long.410-684j lat. bas.30-38^. 



Auburn. 



This is merely an incrassate form of var. Delpontei with 

 strong!}' accentuated scrobiculas. The cells have grown to their 

 full length, as the square apex shows; and a slight further growth 

 has taken place at the suture. The apex in this form is exactly 

 as figured by Delponte, T. xx., f.7. My forma gracilior, I.e., 

 p. 162, is only Ehr. f. minor in the same condition. 



Forma constricta, n.f. (Pl.xi., f.U). 



Forma latitudine ut in var. Delponiei; semicellulis ut in var. 

 constricto conformatis; apicibus rugis granulisve ornatis. Long. 

 518-750; lat.bas.30-39; constr.24-31; centr.26-34; ap.l6-27/x. 



Aubiirn(7, 10, 21), Botany(108, 109). 



