April 1892.] THE BOTANICAL SOCIETY OF EDINBURGH. 425 



EXPLANATION OF FIGURES IN PLATES Ilia, and IV. 



Illustrating Mr Mann's Paper on the Embryo-sac of 

 Myosurus minimus. 



Gynseceum : at the time when a flower expands. 



Fig. 1. Young ovule : Derm., dermatogen. PerihL, periblem. 

 Pier., plerome. A. S., pliysiological archesporium (x. x.) ; 

 X, non-physiological archesporia. 



Figs. 2 and 3, same lettering as in fig. I. Int., integument. 



Fig. 4. a : cell undergoing oblique division. 



Figs. 2 and 4 show increase in the size of the physiological arche- 

 sporium. 



Fig. 5. Monaster stage of archesporium, with 8 chromatin-segments. 



Fig. 6. Later stage, showing inequality in the size of the two cells 

 derived from the archesporium, x and y. 



Fig. 7. The cell " v/" of previous figure precedes its sister-cell (x) in 

 division, and gives rise to the physiological embryo-sac, 

 E. S. 



Fig. 8. The embryo-sac, E. S. Apex of carpellary leaf, C. L. 



Figs. 9*, 9^. Embryo-sac with vacuoles, E. S., and three non-physio- 

 logical embryo-sacs, x-\-x and y. 



Fig. 10, a-d. The gelatinisation of the walls of the physiological 

 and non-physiological embryo-sacs takes place in various 

 degrees. 



Fig. 1 1 . Degeneration of the cell y. Peripheral endonucleoli and 

 a central one in the nucleolus of the embryo-sac, E. S. 



Fig. 12. Cells X and y degenerate. 



Fig. 13*"^. Vacuolation of the embryo-sac, E. S. Its nucleolus 

 with peripheral endonucleoli and a central one. 



Fig. 14. The non-physiological archesporia have given rise to a 

 layer of periblem, Perihl. The cell tj has escaped 

 degeneration. 



Fig. 15. The embryo-sac, E. S., with large vacuole towards its 

 micropylar end, M. E., and the nucleus towards the anti- 

 podal end, A. E. The periblem cells and cells x and y 

 degenerating. 



Fig. 16. The embryo-sac with a central vacuole, v, and an apical 

 (micropylar) nucleus, a.n., and a basal (antipodal) nucleus, 

 h. n. 



Fig. 1 1^'^. The vacuole enlarges, and the apical cell of the embryo- 

 sac becomes cut off from the lower one by a distinct mem- 

 brane, m. 



Fig. 18. Embryo-sac consisting of a micropylar cell, M. C, and an 



