494 POLYMORPHISM AND LIFE-HISTORY IN THE DESMIDIACEjE, 



Figs. 15-20 show the growth of the processes in St. montkulosuynBr^h., 

 and St. forjiculatum Lund., and the development of these desmids out of 

 St. orhiculare \a.r. muticum (Breb. ) All the forms were found in the same 

 gathering(60) in quantity, except fig. 20. 



Fig. 21. — Doc. trabecida \&i\ crenulatum, showing reticulate incrassation 



(x463). 



Plate xiii. 



Fig.l. — Cos. rectangidare var. quadrigemincctum Playf., (a) side ( x 463). 



rig.2.— ,, var. ?jo<a/,m?i, n.var. (a) side ( X 463). 



Fig.3. — ,, var. hexagonumiElty.) W. & G. S. West (a) end 



( X 463). 

 Fig. 4. — Cos. red. var. altim (a) n. var. -t- var. daitatum (b) n.var. (x463). 

 Fig. 5. — ,, var. nodulatum'P\?i^i., f. mmo7\ n.f. ( x G95). 

 Fig. 6. — ,, var. •s«xo?ucMm(Kac.) ( x 4C3). 

 Fig.7. — ,, var. c?/dojoei<m' Playf.) ( x 695). 



Fig.8. — ,, var. subhexagonmn, n.ve^r. (a)-fvar. c)jdopeum{h) ( x 695). 

 Fig, 9. — ,, var. subreniformc, n.var. (a) end ( x695). 

 Fig.lO. — ,, var. renifornie (a) n.var. -f var. cydopeum (b) ( x 695). 

 Fig. 11. — Cos. redangidare var. suhhexagonum forma ( x 695). 

 Fig. 12. — ,, var. re/jawc^2tm(Nord.), f. ( x 463). 



Fig. 13, — ,, var. i^'mmari-jce, n.var. ( X 463). 



rigs.14-15. — ,, var. a;t.s<?-a/e, n.var. ( X 463). 



Fig.l6. — ,, var. oce^^a<tt??i, n.var. ( X 463). 



Fig. 17. — ,, var. ?•o<^t?^rfai^<m, n.var. ( X 695). 



rig.18. — ,, var. pfi<ere/br»ie, n.var. ( X 695). 



Fig. 19.— ,, ,, forma (x 695). 



Fig.20. — ,, var. papillatum, n.v&Y. (x(i95). 



Fig.21. — ,, var. su^ca^Mm'.Nord.) ( X 695). 



Fig.22. — ,, viix. sexangidare{hun6..) i. senilis ( X 4:63). 



Fig.23. — Doc. trahecida var. BrefehUi{Istv.) (a)4-var. tnuicatum(h) ( x 463). 

 Fig.24. — Pen. S2nrostriolatum Barker, forma ( x 463). 



Fig.25. — C;. rostratimi Ehr., (a) + var. Kutzi7igii{Bi-6h.) Klebs (b) ( x463). 

 Fig.26. — Trip, gracile var. superb um[M.aiSkell) Nord. , forma ( x 232). 



Plate xiv. 



Figs. 1-10. — Degeneration in type produced by continuous cell-division due 

 to rise in temperature. The forms are not described or named, as 

 they came about under more or less artificial conditions. (Figs.7-8 

 X 347. The rest x 463). 



Fig.l. — Micr. truncata var. decerndentata(^iig.) , the original cells. 



Figs.2-4. — Results of first, second, and third divisions respectively. 



Fig. 5. — Result of fourth division. Figs. 5, 46 and Qb resemble Micr. incisa 

 Breb., cf. Turn., Alg. E. Ind., T.vi., f.7, 8. 



