472 EXPLANATION OF THE FIGURES. 



FIG. 



3, 4, 5. Spore-mother-cells, with two secondary nuclei, between which a 

 flattened agglomeration of granules is gradually being formed. Fig. 3 

 is x 300, figs. 4 and 5 are x 400. 



6. Mother-cells, with four tertiary nuclei, arranged in the angles of a tetra- 



hedron, x 450. 



7, 8. Mother-cells divided into four special-mother-cells, x 300. 



9. Special-mother-cell divided from its sister-cells, and which has become 

 globular. A spore is just forming in it. x 300. 

 10 Special-mother-cell, with the globular spore. Upon the inner wall of the 

 special mother-cell the first traces of the two wide spiral threads are 

 visible. X 400. 



11. Ripe spore, after the stripping off of the remains of the special-mother-cell 



(the elaters), crushed in sulphuric acid, x 400. 



12. Commencement of germination ; numerous chlorophyll-granules are visible 



in the fluid contents. The central nucleus of the spore has disap- 

 peared ; in the cell two accumulations of granules are seen, each of 

 which surrounds a secondary nucleus, x 400. 



13 — 18, 21. Differently developed germ-plants, .from the beginning to the 

 middle of June, X 300. 



24. Fragment of the margin of an older prothallium (in the middle of July), 

 with a half- developed and a ripe antheridium, both shown in longi- 

 tudinal section, x 200. 



Figs. 19, 20, 22, 23, 25 — 37. Equisetum arvense. 



19, 20, 22. Germinating spores developed in water, x 300. 



23. Somewhat older prothallium, showing the earliest antheridia, x 150. 



25. Portion of the contents of a half-ripe antheridium ; small tessellated cells 



enclose the ellipsoidal mother-cells of the spermatozoa, x 400. 



26. A free mother-cell of spermatozoa, x 300. 



27. A mother-cell, showing the spermatozoon, x 300. 



28. Spermatozoon crippled by treatment with very diluted, watery solution of 



iodine. The stiffened cilia are already visible, whilst the tail still 

 escapes observation by its undulations, x 500. 



29. Spermatozoon quite killed by the same reagent. Its hinder end, already 



somewhat swollen, is in such a position as to enclose a globe of 

 highly refractive matter; this is of rare occurrence. The membrane 

 of the mother-cell is attached to the frontal turns of the thread, x 500. 

 30 — 33. Spermatozoa killed by tincture of iodine. They are far more con- 

 tracted than those whose motions have ended spontaneously or have been 

 terminated gradually by treatment with a very watery solution of iodine. 

 Great differences are apparent in their size, as appears by the comparison 

 of spermatozoa, drawn with the same magnifying power, x 500. 



35. Longitudinal section of a rudiment of an archegonium, x 300. 



36, 37. Similar sections of more developed archegonia; fig. 36 x 200, 



fig- 37 X 300. 



