442 
Lawson . — The Gametophytes , Fertilization and 
EXPLANATION OF FIGURES IN PLATES XXVII-XXX. 
Illustrating Dr. Lawson’s paper on Cryptonuria. 
All the figures were drawn with the aid of the camera lucida. The following oculars and 
objectives were used : — 
Figs, i, 2, 3, 4, 5, 6, 12, 13, 14, 35, 41, 42, 45, Zeiss oc. 1, obj. oil imm. T V 
Fig. 8, Zeiss oc. 3, obj. 7. 
Figs. 9, 10, 11, 15, 39, 40, 59, Zeiss oc. 2, obj. 3. 
Figs. 7, 16, 17, 18, Zeiss oc. 3, obj. 3. 
Figs. 19, 20, 21, 22, 25, 26, 27, 28, 29, 30, 31, 32, Zeiss oc. 3, obj, oil imm. X V 
Figs. 23, 34, 36, 37, 38, 43, 44, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, Zeiss oc. 4, obj. 7. 
Figs. 24, 33, Zeiss oc. 5. obj. 7. 
Figs. 46, 47, 48, Zeiss oc, 5, obj. oil imm, 
Fig. 1. A cross-section of a microspore soon after the separation of the tetrads. Nov. 1, 1903. 
x 1000. 
Fig. 2. A microspore showing the hook-like projection. Drawn from living spore. Dec. 1, 
1903. x 1000. 
Fig. 3. A section of a microspore soon after it reaches the apex of the nucellus. March 7, 
1903. x 1000. 
Fig. 4. The body-cell t., stalk-nucleus s.n., and tube-nucleus t.n . as they are situated at the tip 
of the pollen-tube. June 2, 1903. x 1000. 
Fig. 5. The body-cell undergoing division with the stalk-nucleus situated just below it. June 
9, 1903. x 1000. 
Fig. 6. The two male cells just separating from each other. June 5, 1903. x 1000. 
Fig. 7. A longitudinal section of the apex of the nucellus, showing at least four pollen-tubes 
penetrating the nucellar tissue. May 26, 1902. x 150. 
Fig. 8. A longitudinal section of a pollen-tube with the tip just about to discharge its contents 
in the depression above the archegonium-complex. June 2, 1902. x 300. 
Fig. 9. A longitudinal section of a young megasporangium and integument, showing the method 
of closing of the micropyle. March 7, 1903. x 170. 
Fig. 10. A longitudinal section of two young megasporangia within a single integument. March 
7, 1903. x 170. 
Fig. 11. A longitudinal section of a megasporangium showing the position of the sporogenous 
cells. March 7, 1903. x 170. 
Fig. 12. From a longitudinal section of a megasporangium showing four megaspore-mother- 
cells. March 7, 1903. x 1000. 
Fig. 13. The spindle of the reduction-division of the megaspore-mother-cell. The daughter- 
nuclei are already organized at the poles. March 7, 1903. x 1000, 
Fig. 14. A longitudinal section showing at least fourteen megaspores. The large centrally 
situated spore is probably the only one that germinates. April 6, 1903. X 1000. 
Fig. 15. A longitudinal section of the nucellus, showing a large single embryo-sac with numerous 
free nuclei. May 12, 1902. x 170. 
Fig. 16. A longitudinal section of a young female prothallium, showing the large central vacuole 
and the parietal layer of cytoplasm, in which numerous free nuclei are imbedded at more or less 
regular intervals. May 26, 1902. x 150. 
Fig. 17. The same at a later stage. The free nuclei in the parietal layer of cytoplasm have 
divided and delicate membranes formed between them. The primary cells thus organized are 
open on the side towards the vacuole. The nuclei are arranged at the periphery of the cytoplasm 
and the latter is exposed to the sap of the vacuole. May 29, 1903. x 150. 
Fig. 18. The same at a little older stage, showing the inward growth of the primary prothallial 
