236 Barrett . — Development and Sexuality of some 
21 . Reinsch, P. : Beobachtungen liber einige neue Saprolegniaceen. Jahrb. fur wiss. Bot., xi, 1878, 
pp. 283-311, pi. 14-17. 
22 . SCHRbTER : Kryptogamenflora von Schlesien. Ill, i, 1886, p. 195. 
23 . Sorokin, N. : Materiaux pour la Flore cryptogamique de P Asie Centrale. Rev. Myc., xi, 1889, 
pp. 69-85, 136-52, 207, 208, pi. 78, 83, 85-92 ; xii, 1890, pp. 3-16, 49-61, pi. 93-1 ii- 
24 . Stevens, F. L. : The Compound Oosphere of Albugo bliti. Bot. Gaz., xxviii, 1899, PP* * 49 “ 
176, 225-45, pi. 11-15. 
25 . Wager, H. : The Sexuality of the Fungi. Ann. Bot., xiii, 1899, pp. 575-97. 
26 . Zopf, W. : Zur Kenntniss der Phycomyceten. I. Zur Morphologie und Biologie der Ancylisteen 
und Chytridiaceen. Nova Acta K. Leop. Carol, deutsch. Akad. der Naturf., xlvii, 1884, 
PP- 1 43 ~ 2 3 ^ pk 12-21. 
EXPLANATION OF PLATES XXIII-XXVI. 
Illustrating Mr. Barrett’s paper on Olpidiopsis * 
All figures were drawn with the aid of a camera lucida. The following combinations of 
objectives and oculars were used : Zeiss. apo. obj. 1*5 mm. N.A. 1-30, compen. oc. 18, Figs. 31-5 
and 48-73; same obj., compen. oc. 12, Figs. 23 and 37-9; same obj., compen. oc. 8, Figs. 12-14, 
22, 41, and 47; Zeiss apo. obj. 2 mm. N.A. 1*40, compen. oc. 12, Figs. 1-4, 8-10, 15, and 40; 
Zeiss, apo. obj. 2 mm. N.A. 1-40, compen. oc. 8, Figs. 28-30, 36, and 42-6; Zeiss' apo. obj. 
3 mm. dry, compen. oc. 12, Figs. 11, 17, 18, 24, and 25; 2/3 in. obj. and 1/2 in. oc., Fig. 26; 
1 /8 in. obj. and 1 in. oc., Fig. 27. 
PLATE XXIII. 
Fig. 1. Zoospores of Olpidiopsis luxurians. a, Drawn from a living zoospore. All others 
from stained preparations. 
Fig. 2. Zoospores of Olpidiopsis Saprolegniae. a, From a living zoospore. All others from 
a stained preparation. 
Fig. 3. Zoospore resting on an Aphanomyces hypha preparatory to entrance. 
Fig. 4. Contents of the zoospore in the hypha, the empty spore wall outside. 
Fig. 5. Germinated zoospore of 0 . luxurians on an empty sporangium of Aphanomyces laevis. 
Fig. 6. Germinated zoospore of 0 . luxurians on an old, but still living, hypha of Aphanomyces 
laevis. 
Fig. 7. A young developing sporangium of 0 . luxurians five hours after infection. 
F!g. 8. Zoospore of 0 . Saprolegniae beginning to discharge its contents into the hypha of 
Saprolegnia ferax. 
Fig. 9. Same zoospore as in Fig. 8, process nearly completed. 
Fig. 10. Germinated zoospore of Aphanomyces laevis infected by 0 . luxurians. 
Fig. 11. Young developing sporangium of 0 . luxurians . 
Fig. 12, A sporangium of 0 . luxurians , showing the homogeneous ground substance containing 
small granules and a few fat globules. 
Fig. 13. Same sporangium as in Fig. 12, three hours later. 
Fig. 14. Same as Fig. 12, twenty-four hours later. Zoospores formed and exit tube beginning 
to develop. 
Fig. 15. Zoospores of 0 . vexans from a stained preparation. 
Fig. 16. Intercalarily formed sporangium of 0 . luxurians showing two characteristic exit tubes. 
Fig. 17. Sporangium of 0 . luxurians , showing the recently developed membrane, vacuolate 
nature of the protoplasm, and the radiate character of the host protoplasm. 
