26 Lawson . — The Gametophytes , Archegonia , Fertilization , 
Webber, H. J. (’97) : Peculiar Structure in the Pollen Tube of Zamia. Bot. Gaz. xxiii, p. 453. 
The Development of the Antherozoids of Zamia. Bot. Gaz. xxiv, p. 16. 
Notes on the Fecundation of Zamia and the Pollen Tube Apparatus of 
Ginkgo. Bot. Gaz. xxiv, p. 225. 
(’01) : Spermatogenesis and Fecundation of Zamia. U. S. Dept. Agri. Bur. of Plant 
Industry. Bull, ii, 1901. 
Woycicki, Z. (’99): Fertilization in the Coniferae. Warschau, 1899. Reviewed in Jour. Roy. 
Micro. Soc. p. 482, 1900. 
EXPLANATION OF FIGURES IN PLATES I -IV. 
Illustrating Dr. Lawson’s Paper on Sequoia sempervirens. 
All the figures refer to Sequoia sempervirens , and were drawn with the aid of the Camera lucida. 
For the finer cytological details, Zeiss’s homogeneous immersion obj. ^ apert. 1-25 with compensating 
ocular No. 6, and for the lower magnifications obj. and £ and ocular No. 4, were used. 
Fig. 1. A microspore as it appeared about two weeks before pollination, showing the single 
centrally situated nucleus. Material collected Dec. 15, 1901. x 900. 
Fig. 2. A microspore at the time of pollination, showing the large centrally situated tube-nucleus 
{t. n.) and the smaller laterally situated generative nucleus ( g . n.). Jan. 1, 1902. x 900. 
Fig. 3. A longitudinal section of the ovule, showing the relative height of the macrosporangium 
and the integument. The micropyle is nearly closed, and the pollen-tubes are shown growing down 
between the sporangium and the integument. Within the sporangium six macrospore mother-cells 
are represented. Material collected March 12, 1902. x 125. 
Fig. 4. A pollen-tube penetrating the nucellus near the top. The generative nucleus has 
divided, so that there are now three free nuclei in the tube. The large tube-nucleus ( t . n.) is in 
advance of the stalk- ( S.n .), and the body- ( B . n.) nuclei, x 750. 
Fig. 5. The lower part of the pollen-tube, showing the body-cell (p. c.) fully organized and the 
stalk-nucleus lying close beside it. Material collected June 12, 1902. x 750- 
Fig. 6. The tip of the pollen-tube containing the tube-nucleus ( i . n.), the stalk-nucleus ( S . n.) } 
and the large body-cell (b. c.) in the rear. Material collected June 15, 1902. x 750. 
Fig. 7. The body-cell undergoing division. The daughter-nuclei are organized and are 
connected by a series of kinoplasmic fibrils. The fibrils curve out toward the cell- wall in prepara- 
tion for cell-plate formation. Material collected June 29, 1902. x 750- 
Fig. 8. Two male cells as they appear immediately after the division of the body-cell. At this 
time they are flat on one side, and each contains a large centrally situated nucleus. Material 
collected June 29, 1902. x 750. 
Fig. 9. A longitudinal section through the central portion of the macrosporangium, showing six 
macrospore mother-cells. The cytoplasm of these cells is very dense and granular. The nuclei are 
comparatively large, and judging from the condition of the chromatin they are preparing for mitosis. 
Material collected March 2, 1902. x 800. 
Fig. 10. Section same as Fig. 9. The macrospore mother-cells are undergoing division. Two 
spindles of the reduction-division are shown. March 12, 1902. x 800. 
Fig. 11. A longitudinal section through the macrosporangium, showing eight germinating 
macrospores or young prothallia. Three of the prothallia are larger than the others, and each 
contains two nuclei. Their growth is directed towards the chalaza. April 25, 1902. x 175. 
Fig. 12. A longitudinal section, showing two young prothallia after repeated nuclear division. 
The free nuclei are distributed along a central strand of cytoplasm which extends from end to end of 
the prothallium. April 25, 1902. x 175. 
Fig. 13. A longitudinal section of a primary prothallium at a later stage, showing the very large 
central vacuole and parietal layer of cytoplasm in which the free nuclei are distributed. June 8, 
1902. x 175. 
