296 BOTANICAL GAZETTE [ocxober 



4. Fischer, A., Saprolegniineae, in Rabenhorst's Kryptogamenflora, i'':3io- 

 383. figs. 13. 1892. 



5. Humphrey, J. E., The Saprolegniaceae of the United States. Trans. 

 Amer. Phil. Soc. 17:1-148. pis. 7. 1893. 



6. Leitgeb, H., Neue Saprolegnieen. Prings. Jahrb. Wiss. Bot. 7:357-387. 

 pis. 22-24. 1869. 



7. LiNDSTEDT, K., Synopsis der Saprolegnniaceen und Beobachtungen iiber 

 einiger Arten. Berlin, pp. 69. pi. 4. 1872. 



8. MiNDEN, M. VON, Saprolegniineae, in Kryptogamenflora der Mark Bran- 

 denburg, s^ : 209-600. 1912. 



9. PiETERS, A. J., New species of Achlya and Saprolegnia. Bot. Gaz. 60: 

 483-490. pi. I. 1915. 



10. TlESENHAUSEN, M., Beitragc zur Kenntnis der Wasserpilze der Schweiz. 

 Arch. Hydrobiol. Planktonk., Biol. Sta. Plon. 7^:261-308. 1912. 



11. Weston, W. H., Observations on an Achlya lacking sexual reproduction. 

 Amer. Jour. Bot. 4:354-367. pi. 18. 1917. 



12. ZoPF, W., iiber eine Saprolegniee mit einer Art von Erysipheenahnlicher 

 Fruchtbildung. Beitrage Physiol. Morphol. Nied. Org. 3:48-59. pis. 2, 3. 

 1893. 



EXPLANATION OF PLATE XXIII 



The figures were drawn from living material at the level of the stage 

 with the aid of an Abbe camera lucida. The approximate magnification of 

 the combination of lenses used is given in each case, but appUes to the original 

 figures, which have been reduced to about two-thirds of their diameter in 

 reproduction. 



Fig. I. — Two successively formed sporangia, the terminal empty, showing 

 "cell-net" structure; second still containing spores; X550. 



Fig. 2. — Sporangium developed from starved hypha, showing incomplete 

 uniting of spore walls; X5S0. 



Figs. 3-7. — Stages in emergence of zoospore from sporangiospore; X 1400. 



Fig. 8. — Zoospore after liberation; oblique later view; X1400. 



Fig. 9. — Same just starting to swim away; side view; X1400. 



Fig. id. — 'Encysted zoospore (cystospore) ; X1400. 



Figs. 11-13. — Stages in emergence of zoospore from cystospore; X1400. 



Fig. 14. — Zoospore just after emerging; side view; X1400. 



Fig. 15. — Same just starting to swim away; looking down on grooved 

 surface; X1400. 



Figs. 16-17. — Cystospore germinating by formation of hypha; X1400. 



Fig. 18. — Germination of sporangiosp>ores in situ by hyphae; X550. 



Fig. 19. — Separation of sporangium from its hypha by rupture of sporan- 

 gium wall at base; X1400. 



