488 POLYMORPHISM AND LIFE-HISTORY IN THE DESMIDIACE^E, 



to be quite accurate. Thex'e are three pairs of processes down 

 each side; there should be three, therefore, (besides the sublateral 

 ones) in end-view. Tlie two denticulations at the apex of his 

 figure are the tips of the two apical verrucae at the head of the 

 foreshortened angle. 



A mixed form of the above and var. hifarium forma was noted. 



Var. AGGERATUM(Playf.), ante, 1907, Pl.iv., f.21. 



Long. 28; lat. s.sp. 30/i. 



Botany. 



Both front and end-views are quite correct. Var. aggeratum 

 is a young form of var. forficulatum, and develops into it through 

 var. aculeatum. 



Forma. (Pl.xii., f.l96). 



Forma lateribus apicibusque magis rotundatis, glabris; apicibus 

 quam levissime deplanatis; angulis lateralibus interdum aculeo 

 interdum nullo prseditis. 



Common round Sydney. This form, like var. granulosum, is 

 common to both the hifarium and forficulatum lines of develop- 

 ment. Dimensions noted as yet only in : — 



Forma mixta. — var. hifarium f. et var. aggeratum f., Pl.xii., 

 f.l9. Long, c.proc. 35, s.proc. 32; lat. var. hifar. c.proc. 38, s.proc. 

 26; lat.var. agger, c.sp. 34, s.sp. 28^. 

 Guildford(60). 



St. SEXANGULARE(Bulnh.) Ptabenh. 



Descriptions of variations illustrating the development of 

 pi'ocesses. 



St. sexangulare var. STELLiNUM(Tarn.). 



Synonyms, St. stellinum Turn., Alg. E. Ind., PL 15, f.6; St. 

 sexangulare f. 5-radiata immatura Playf., an^e 1907, p. 185, PI. v., 

 f.ll. Lat. c.proc. 7 5- 120^. 



Collector. 



The processes become shorter and stouter as the denticulations 

 form. 



