476 EXPLANATION OF THE FIGURES. 



fig. 



5. Two spore-mother-cells, and some of the small mucilaginous cells out of 



the inner cavity of a sporangium destined to form a large spore, X 300. 



6. One of the young, large spores, with a set of four abortive special-mother- 



cells, from a similar sporangium, X 300. 



7. A similar sporangium, cut through longitudinally, at the same stage 



of development, X 200. 



Tigs. 8 14. Pilularia rainuta. 



8. Longitudinal section of a very young fruit, x 100. 



9. An almost ripe fruit, cut transversely close above the lowest sporangia, 



x 10. 



10. Mother-cell of large spores divided into four special-mother-cells, X 400. 



11 14. Stages of development of large spores ; by the side of figs. Hand 12 

 abortive mother- cells from the same sporangia are drawn. Fig. Jl is 

 X 300, fig. 2 is X 150, and figs. 13 and 14 are x 250. 



Pigs. 15 24. Marsilea pubescens. 



15. Outlines of a large spore just escaped from the opening fruit, in longitudi- 



nal section. 



16. Apex of the same (the gelatinous covering in this and the following figures 



is not shown). The primary spore-membrane and the lenticular cell 

 occupying its apex have been carefully drawn out from the introversion 

 of the inner layer of the exosporium. X 300. 



17. Commencement of germination. In each lenticular cell two globular nuclei 



are seen in the place of the primary one. X 300. 



18. Bicellular rudiment of a prothallium, laid bare by means of two parallel 



longitudinal sections through the spore. The primordial utricles of the 

 cells are contracted by the action of a concentrated solution of caustic 

 potash, x 400. 



19. Lateral view of a four-celled rudimeut of a prothallium, x 400. 

 20 21. Lateral view of a more developed prothallium, x 300. 



22. Prothallium ready for impregnation, in longitudinal section, x 300. 



23. Half-developed prothallium, seen from above, x 300. 



24. The same from below, x 300. 



Pigs. 25 32. Salvinia nutans. 



25. Microsporangium cut transversely ; the antheridia (microspores which have 



shed their outer membranes) are falling out, X 200. 



26. A single microspore less developed, x 200. 



27 28. Cellular bodies (antheridia) squeezed out of the sporangia with small 

 spores in the middle of March, X 300. 



29, 30. Riper antheridia already half emptied, x 300. 



31. Spermatozoon with attached mother-cell, X 500. 



32. Spermatozoon killed by iodine, X 500. 



