804 welwitsch's afbioan freshwater alg^. 



ericetorum are to be found extending over wide patches of almost 

 bare sand, round such plants as Drosera, Carices, &c. These 

 interlacing masses have great absorptive capacity, greedily taking 

 up water; it is also highly probable that they protect and render 

 the growth of other plants more possible by regulating the moisture 

 of the surface soil. It is interesting to note that Zygnema ericetorum 

 is found intermixed in small quantity with the Porphtjrosiphon 

 Notarisii which covers such extensive areas in Angola. 



Description of Plates. 

 All the figures are x 520, except fig. 2, t. 365, which is x 120. 



Tab. 365. — Fig. 1-2. Pohjchlamydnm insigne, n. gen. et sp. 3-C. Protc- 

 reiidothri.v scolecoidea, n. gen. et sp. 7-8. (Edogonium hiiiUense, n. sp. 9. 

 Closterium peracerosum Gay, var. cethiopicum, n. var. 10. Pleurotcenium sparsi- 

 punctatum, n. sp. 11. Cosmarhun cequinoctiale, n.sp. 



Tab. 366. — Fig. 1. Micrasterias tropica Nordst., forma. 2. M. tropica 

 Nordst., var. elegans, n.var. 3. 21. tropica Nordst., var. cratisa, n. var. 4. it/. 

 polonica'Wesi & G. S. West. 5-C. M. robusta, n.sp. 7. M. arcuata Bail. var. 

 siibpinnatifida, n. var. 8. Euastrum hinale (Turp.) Ehrenb. var. angolense, n. var. 



9. E. subdivaricatum, n.sT^. 10. E. tetragomim, n.sii. 11-12. E. acmou, n.sp. 

 13. E. acmon v&v. claiisum, n.vav. 14. E. liolosclierum, n.sp. 15-16. E. Ituil- 

 lense, n. sp. 17. E. bimorsuiit, n. sp. 18. E. siibinerme, n. sp. 19. E. sub- 

 personatum, n.sp. 20. Cosmarium Baileiji Wolle, var. angolense, n.var. 21. 

 C. Oocystiduin, n.sp. 



Tab. 367. — Fig. 1. Cosmarium colonoplwrunt, n.sp. 2. C. 11 elwitscJdi, n.sp. 

 3. C. centrotapliridium, n.sp. 4-6. Ditto, central scrobiculations. 7. C. ango- 

 lense, n.sp. 8. C. multiordinatiim, n.sp. 9. C. tetrasticlnoii, n.sp. 10. C. te- 

 trastieliuvi var. depauperatum, n.var. 11. C inediogemmatuin, n.sp. 12. C. 

 ligonifor me, n.sp. 13. C. callistum, n.sp. 14. C. pseudotaxichondraml^o\:As\j., 

 var. africanum, n. var. 15. C. huilleme, n. sp. 16. C. viucronatum, n. sp. 

 17. C. bilunatiim, n. sp. 18. C. meteorotwtinn, n. sp. 10. C. trifossiDU, n. sp. 

 20. C. (Bthiopicum, n.sp. 21. C. ma.vimum (Borg.) nob., \ax. minor, n.\a.r. 



Tab. 368.— Fig. 1. Cosmarium africanum, n. sp. 2-3. C. galeatum, n. sp. 

 4-5. C. Norimbergense Reinsch, forma elongata. 6. C. Iccve Rabenh. var. ?»('«( - 

 7/u(ni, n. var. 7. C. rt//iHe Racib. var. fl/rtcfuium, n.var. 8. C. submamilliferum, 

 n.sp. 9. C. Portianum Arch. \a,v. orthostichum, Hchmidle. 10. C. concentricum 

 W. B. Turn. var. radiatum, n.var. 11. C. subtriordinatum, n.sp. 12. C. Li- 

 bongense, n.sp. 13. C. repandum Nordst. 14. Xanthidium subtiilohum, n.sp. 

 15. A', cristatum Breb. var. tropicum, n. var. 16. X.fasciculatum Ehrenb. forma. 

 17. Staurastrum huillense, n.sp. 18. S. scrobiculatum, n.sp. 19. S. micron 

 West & G. S. West, var. angolense, n. var. 20. ,S'. Gurgeliense Schmidle, var. 

 tropicum, n.\a,v. 21. S. cassidum, n.sp. 22. ,S'. angolense, n.sp. 23. Penium 

 variolatum, n. sp. 24. Closterium pusiUum Hantzsch, var. suhrectum, n. var. 

 25. Tetmemorus ^fissus, n. sp. 26-31. Ichthyuccrcus angolensis, n. gen. et sp. 

 32-34. Docidium trigeminiferum, n.sp. 



Tab. 869.— Fig. 1. Staurastrum IVehcitschii, n. sp. 2. S. Corbula, n. sp. 

 3. S. Corbula var. pulchrum, n.var. 4. »S'. actinotu)n, n.sp. 5. S. actinotum 

 var. simpler, n.var. 6. S. pentateuchophorum, n.sp. 7. S. tridens-Neptuni, 

 n.sp. 8. S, heteroplophorum, n.sp. 9. S. heteroplopliorum var. latum, n.var. 



10. S. Pseudohystrix, n. sp. 11. S. tripodum, n. sp. 12. S. egregium, n. sp. 

 13. S. cerastoides, n. sp. 14. S. crux-alternans, n. sp. 15-1(). -S'. quadri- 

 dentatum, n.sp. 17. S. areolatum, n.sp. 



T.^B. 370.— Fig. 1-2. Athroocystis ellipsoidea, n.(:^en. etsp. 3-4. Pgxis2)ora 

 viirahilis, n. gen. et sp. 5-9. Temnogametuin Jwterosporum, n. gen. et sp. ; 7, 

 scalariform conjugation between two specially cut-otf cells; 8-9, lateral conju- 

 gation ; s, f,', spores produced by scalariform conjugation ; I, spore produced by 

 lateral conjugation. 10-17. Camptothrix repcns, n. gen. et sp. ; 10-12, older 

 filaments; 13-17, younger filaments. 18-19. Co>imnnumalatumK\xch.y&x.sub- 

 oblongum,n. var. 20. Staurastrum elegantissi)num Johnson, var. 7-eductum, n. var. 



