Bliss. — A Contribution to the Life-history of Viola . 163 ' 
EXPLANATION OF PLATES XVII-XIX. 
Illustrating Miss Bliss’s paper on the Life-history of Viola. 
All figures were drawn with an Abbe camera lucida. The degree of magnification is indicated 
in the description of each figure. The portion of a figure nearest the micropylar end of the ovule is 
always towards the top of the plate. The abbreviations used in describing the figures are to be 
defined as follows: ant., antipodals; d.a.c., definite archesporial cell ; e., egg; emb.s., embryo-sac ; 
emb., embryo; end., endosperm; g.n., generative nucleus; i.i., inner integument ; m.m.c., mega- 
spore-mother-cell; meg., megaspore ; nc., nucellus ; n., nucleus; mi., nucleolus; o.i., outer integu- 
ment; p.t., pollen-tube; p.g., pollen-grain; p.meg ., potential megaspore; p.a.c., primary arche- 
sporial cell ; s.n., sperm nucleus ; s.nu., sperm nucleolus ; Syn., synergids ; t.n., tube nucleus ; tap., 
tapetum. 
PLATE XVII. 
Fig. 1. Section of upper portion of ovule, showing origin of archesporial cell. x 960. 
V. odorata. 
Fig. 2. Section of upper portion of ovule, showing first division of primary archesporium to form 
tapetal cell, x 960. V. odorata. 
Fig. 3. Section of nucellus, showing further divisions in tapetum and growth of definite arche- 
sporial cell, x 960. V. cucullata. 
Fig. 4. Tip of nucellus, showing late telophase of first division, x 960. V. pedata . 
Fig. 5. Second division of archesporial cell, x 960. V. cucullata. 
Fig. 6. Axial row of four cells arranged in a vertical row. x 960. V. cucullata. 
Figs. 7, 8. Axial row of four cells, showing oblique walls between the cells, x 960. V. 
cucullata. 
Fig. 9. Tip of nucellus, showing axial row of four cells, upper three disintegrating, lower 
developing to form embryo-sac. x 960. V. cucullata. 
PLATE XVIII. 
Fig. 10. Axial row of four cells, third developing to form embryo-sac. x 960. V. cucullata. 
Fig. 11. Axial row of four cells, second developing to form embryo-sac. x 960. V. cucullata. 
Fig. 12. Section of ovule showing two-celled embryo-sac. x 960. V. pedata. 
Fig. 12 a. Embryo-sac of Fig. 12. x 960. 
Fig. 13. Four-celled embryo-sac. x 960. V. cucullata. 
Fig. 14. Eight-celled embryo-sac. x 960. V . Jimbriatula . 
Fig. 15. Mature embryo-sac after fusion of polar nuclei, antipodals disintegrating, x 960. 
V. pedata. 
Fig. 16. Unusual development of antipodals. x 960. V. cucullata. 
Fig. 17. Antipodal portion of embryo-sac, showing slight haustorial development, x 960. 
V. pedata. 
Fig. 18. Mature pollen-grain, showing tube-cell and fusiform generative cell. x 960. 
V. cucullata. 
PLATE XIX. 
Fig. 19. Fusion of sperm with endosperm nucleus, x 1,200. V. cucullata. 
Fig. 20. Mature embryo-sac before fusion of sexual nuclei, showing telophase in the first division 
of the endosperm nucleus, x 960. V. cucullata. 
Fig. 2 1 . Embryo-sac, showing fertilization of the egg and four endosperm nuclei. 
Fig. 21 a. Upper portion of Fig. 21. x 960. V. cucullata. 
Fig. 22. Embryo-sac, sperm, and egg nuclei not yet in contact. Fourth division of endosperm 
completed, x 490., V. cucullata. 
Fig. 23. First division of the egg. Late anaphase, x 1,200. V. pubescens. 
Fig. 24. Two-celled embryo, x 960. V. Jimbriatula. 
Fig. 25. Three-celled embryo, x 960. V. cucullata. 
Fig. 26. Four-celled embryo, x 960. V. cucullata. 
Fig. 27. Multicellular embryo, globular in outline, showing sheath of endosperm, x 960. 
V. pubescens. 
M 2 
