OF FERNS FROM THEIR SPORES. 137 



Fig. 13. Greatly enlarged view of two cells of a prothallium, showing the position and appearance of the 

 green chlorophyll globules. 



Fig. 14. Another cell, occurring isolated among others of the ordinary character, in which the large chlo- 

 rophyll globules have acquired a parenchymatous appearance from mutual pressure. 



Fig. 15. Chlorophyll globules very much magnified, exhibiting (starch) granules within, and apparently 

 a membranous coat. 



Fig. 16. Magnified fragment of & prothallium from the neighbourhood of the anterior notch (under sur- 

 face), bearing several antheridia, some imperfect, one ripe, two effete : the lowest is seen side- 

 ways, and the structure is made evident by the brown colour of the membrane of the cavity 

 which has discharged its spermatozoids. 



Fig. 17. Two cells, from which antheridia are being formed, by budding out from the lower faces ; the 

 left-hand one is the youngest and contains a little chlorophyll ; in the right-hand one the chlo- 

 rophyll has given place to dense protoplasm. 



Fig. 18. Marginal antheridia, almost ripe. 



Tab. XV. 



Fig. 19. Antheridia in various stages; the brown one has discharged its spermatozoids. a. represents a 

 brown peculiar thickening of the cell-walls, with the formation of bars or striae, occasionally met 

 with in old prothallia. 



Fig. 20. Antheridium, seen by looking down upon it. 



Fig. 21. Side view of an antheridium, in which the protoplasm is just beginning to subdivide to form the 

 sperm- cells. 



Fig. 22. A more advanced specimen. 



Fig. 23. Nascent sperm-cells, from the preceding figure. 



Figs. 24-26. Antheridia, seen from above, showing the subsequent stages of development of the sperm- 

 cells. In figs. 24 & 25 the annular enveloping cell is still perceptible ; in fig. 26 its inner mem- 

 brane is pressed out and applied against the outer one, and invisible. 



Figs. 27-29, 31, 32. Various stages of development of marginal antheridia from young prothallia, produced 

 from buds arising on old sterile prothallia. 



Fig. 33. Hairs found near the notch on the under face of perfect prothallia. 



Fig. 34. Side view of an antheridium distended with perfect sperm-cells. 



Fig. 35. Antheridia, seen from above, focused to show the condition of the ripe sperm-cells within. 



Fig. 36. An antheridium, burst by pressure, emitting its sperm-cells. 



Fig. 37. Sperm-cells, one with a nucleus, before the spiral filaments or spermatozoids are perceptible in 

 them. 



Fig. 38. Side view of an antheridium, with the spermatozoids escaping freely, bursting the sperm-cells 

 within the cavity of the antheridium. 



Fig. 39. Sperm-cells, not quite ripe, exhibiting the spermatozoids coiled up in them. 



Fig. 40. Spermatozoids in motion, seen in different positions ; the halo of light around each is the result 

 of the movement of the cilia, which is so rapid that they are invisible. 



Fig. 41. Spermatozoids, arrested by solution of iodine, exhibiting the cilia. 



Fig. 42. Peculiar conditions of the spermatozoids, seen in one instance only : the left-hand figure repre- 

 sents one uncoiled ; the right-hand one appears to have a capillary tail, since it dragged the 

 little mass of mucilage represented along with it. 



Figs. 43 & 44. Spermatozoids, imperfectly developed and incapable of extricating themselves from the 

 sperm-cells, but seen in motion. 



