258 EXPLANATION OF THE PLATES. 



Fig. G. Closterium Leihleinii, Ktz., magnified 2C0 diaraoters. 



Fio'. 7. Telmemorus cjigantciai, Wood., nuignifiod 2G0 diameters. 



Fig. 8. Telmemorus granulatua (Breb.), magnified 450 diameters. 



Fig. 9. Pleurotsenium IVabecula (Ehrb.), magnified IGO diameters. 



Pig. 10. Spirotsenia hryophila (Breb.). 



Fig. IL SjnrOi 'ina condeiiKala, Breb. 



Fig. 12. Eyahitheca dLssilieris, Breb. 



Fig. 13. Bidi/mnpriiim GrcviUii, Ktz. 

 Fig. 13 a. End view. 



Fig. 14. Gosmariuni Bulrijlis (Bory.), magnified 460 diameters. 



Fig. 15. Gosmariuni Caeumis, Corda. 



Fig. 15 d. A frond in whieh the neck or isthmus has begnn to elongate previous to division. 

 Fig. 15 b. An abnormal frond whieh has attempted division, but in which the inner semiceljs of 

 the uew frond have failed to form perfectly and to separate. 



Fig. 16. Euaalrum mulliluhaliim, Wood ; front view. 



Fig. n. ]\[icrastcrias Americana (Elirb.). 



Fig. 18. Coamarium Mcnerjhcnii, Breb., magnified 750 diameters. The sinus sbonld be very 

 narrow but distinct, instead of being absent as in the figure. 



Fig. 19. Spirogyra Weheri, Ktz., portions of conjugating filaments, magnified 260 diameters. 



Fig. 19 a. A portion of a sterile filament, magnified IGO diametei's. 



Fig. 19 b. Conjugating cells with nearly mature spores, magnified 260 diameters. 



Fig. 20. Closterium juncidum, Ralfs., magnified 260 diameters. 



Fig. 21. Cosmarium margariliferam (Turp.), magnified 460 diameters. 



PLATE XIII. 



Fig. 1. Front view of Euastrum Ralfsii, Rabenh., magnified 450 diameters. 



Fig. 2. Front of Euastrum elegans, Breb., enlarged 750 diameters. 



Fig. 3. Front view of Euastrum binale (Turp.), magnified 750 diameters. 



Fig. 4. Front view of Micrasteria dispulata, Wood, drawn from a Philadelphia specimen. 



Pig. 4 a. The same after a figure drawn by Dr. Jos. Leidy, from a Newport specimen. 



Fig. 5. Micrasterias furcata, Agardh., front view, magnified 260 diameters. 



Fig. 6. Front view of Micrasterias denticulata, Breb., magnified 260 diameters. 



Fig. 7. Micrasteria Jenneri, Ralfs. Front view. 



Fig. 8. Slaurastrum orbiculare (Ehrb.). Front view. 



Fig. 9. Slaurastrum dejecium, Breb. Front view, magnified 750 diameters. 



Fig. 10. Slaurastrum ])unctalatum, Breh. Front view. 

 Fig. 10 a. View from the ape.\. 



Fig. 11. Front view of Slaurastrum Lewisii, Wood, magnified 750 diameters. 



Big. 12. Front view of Slaurastrum jwlytrichum, Perty. 



Fig. 13 a. Front view of Slaurastrum munitum, Wood. 

 Fig. 13 0. End view of the same. 



Fig. 14. Gosmarium 2yyramidalnm,'[\voh\s^on. Front view. 



