476 Ferguson . — The Development of the Egg and 
EXPLANATION OF FIGURES IN PLATES XXIII, 
XXIV, AND XXV. 
Illustrating Miss Ferguson’s paper on Fertilization in Pinus Strobus . 
All figures were drawn with the aid of the Abbe camera lucida, projection 
14*3 cm. A Zeiss microscope was used, the lenses being combined as follows: 
Figs. 8-12, 41, 75-82 with ocular 4 and 16 mm. objective; Figs. 1-7, 
38-40, 42-50 with comp, ocular 12? and objective as before ; Fig. 33 with 
ocular 4 and 4 mm. objective; Figs. 13-32, 34-36, 51-74, 77 b, 78 b, 79 b, 
80 b, 81 b, and 82 b with ocular 4 and 2 mm. homo, immer. objective; Figs. 37 a~ 
37 g, and 88-90 with comp, ocular 12 and 2 mm. homo, immer. objective. The 
amount of magnification accompanies the description of each figure. The 
drawings were reproduced without reduction. The lettering of the figures is to be 
interpreted thus: prothallium (pri), ventral canal-cell (y. c.), neck-cells (it. c .), 
egg-nucleus (e. n.), sperm-nucleus (s. n.), sperm-cytoplasm (j. c.), vegetative 
nucleus (v. n.), stalk-cell (st. c.), starch (s/t.), cytoplasm from pollen-tube ( c.p . t.), 
nutritive spheres (; n.s .), primary nucleolus ( py . ns.), secondary nucleolus (sy. ns.). 
All the figures, with the exception of Figs. 33 and 80 b, have been given their 
normal position, as nearly as it was possible to do so, on the plates, i. e. they are 
so placed that the primary axis of the ovule would be parallel with longer axis of 
the half-plates ; and the portion of a figure nearest to the micropylar end of the 
ovule is always toward the top of the plate. Unless otherwise stated the figures 
represent stages in the development of Pinus Strobus. 
PLATE XXIII. 
Figs. 1-7. Stages in the early development of the archegonium. x 160. 
Figs. 8-1 1. Later stages in the growth of the archegonium. x 70. 
Fig. 12. Mature archegonium. x 70. 
Fig. 13. Nucleus of the central cell shortly before its division, x 540. 
Figs. 14-18. Prophases in the division of the central cell, x 540. Nos. 16 and 
18, Pinus austriaca. 
Fig. 19. Cross-section of the ventral canal-cell soon after segmentation of the 
chromatic spirem. x 540. 
Figs. 20-21. Disappearance of the nuclear membrane and establishment of the 
achromatic spindle, x 540. 
Figs. 22-29. Separation of the half-chromosomes and formation of the daughter- 
nuclei. x 540. Nos. 24 and 29, Pinus austriaca . These figures show some of 
the variations occurring in the mitotic figure for this division, and the corresponding 
variations in the structure of the nucleus of the ventral canal-cell. 
Figs. 30-32. Later history of the ventral canal-cell and early stages in the 
development of the egg-nucleus, x 540. 
Fig. 33. Division of the central cell, showing also the lower portion of a pollen- 
tube which has already reached the endosperm, x 230. Pinus montana , var. 
uncinata. 
Fig. 88. The primary nucleolus from a mature egg-nucleus with secondary 
nucleoli clustered about it, and evidently being formed by it. The primary 
nucleolus has a great affinity for stains at this time, x 1200. 
