263 
of Pilularia globulifera , L. 
Fig. 3. Vertical section through, an embryo composed of four cells. The first 
wall (basal wall) is here and in the succeeding figures indicated by the number 1, 
the second (quadrant-wall) by II. The direction of the arrow indicates the anterior 
end of the embryo. 
Fig. 4 vertical, Fig. 5 transverse section through somewhat older embryo. Fig. 4, 
alcohol-borax-carmine-preparation. Fig. 5, alcohol-safranin-preparation. 
Figs. 6-8. A series of three transverse sections through a very advanced embryo 
48 hours after sowing the spores. /, leaf-quadrant ; r, root ; s, stem ; f, foot. 
Fig. 9. Series of four vertical sections through an embryo three days from the 
commencement of germination. 
Figs. 10, 11. Two vertical sections through an embryo of four days 1 . 
Fig. 12. A similar section, but showing better the apical cell of the root. 
Fig. 13. Median transverse section through an embryo of four days. 
Fig. 14. Two other sections of the same embryo, a, above; b, below the 
quadrant-wall. 
Fig. 16. Three transverse sections of an embryo of four days, but somewhat 
further advanced. The apical cell of the root has already formed the first cap-cell. 
Fig. 15. A still more advanced embryo. Vertical median section. 
Figs. 17-21. Series of vertical sections through an embryo of five days. Fig. 17, 
the leaf. Fig. 18, stem. Figs. 19-21, root. In 17 b may be seen the beginning 
of the vascular bundle of the leaf. 
Fig. 21 a. Longitudinal section through the root of an embryo of the same age. 
Fig. 22. Series of four transverse sections of an embryo of seven days (not as far 
advanced as usual). In b and c are seen the indications of the vascular bundles 
of the root and leaf. 
Fig. 23. Median longitudinal section of an embryo of eight days, still surrounded 
by the pro thallium-cells and showing the macrospore, x about 100. 
Fig. 24. The basal part of the same embryo, x 300. i, intercellular spaces. 
r, apex of the root, s, apex of the stem. 
Fig. 25. Second leaf of the same embryo. 
Figs. 26-29. Details of the structure and division of the nuclei of the young 
embryo. All examined with a oil-immersion lens. Fig. 26 from a two-celled 
embryo. Fig. 27, embryo of four days. Fig. 28, embryo of five days; alcohol- 
safranin-preparation. Fig. 29, embryo of eight days. 
PLATE XV. 
Fig. 1. Transverse section through the apex of the stem of an embryo of nine 
days, a, apical cell of the stem. Z 2 , the second leaf. The vascular bundle of 
the first leaf lies above, x 300. Alcohol-gentian-violet-preparation. 
Figs. 2-5. Series of transverse sections through the root of an embryo of the 
same age. a , b, sections through the root-cap, the others through the root itself. 
i, intercellular spaces. Alcohol-Bismarck-brown-preparation. x 300. 
1 The expressions four days, five days, etc., will be understood to mean from the 
time the spores were first placed in water. 
