AMERICAN JOURNAL OF BOTANY 
[Vol. io, 
162 
studied by him, but shows in transverse section many more than that 
number. Figure 47 shows a cross section of the neck of a nearly mature 
archegonium at a distance of about 20 m from its tip. Figure 48 shows a 
similar section of the same archegonium at a distance of about 50 m from the 
tip. Figure 49 shows the cross section of the same archegonium just above 
the venter and about 80 M from the tip. Figure 50 shows the section through 
the egg and venter at a distance of about iiom from the terminal end. 
The development of the embryo seems to furnish a stimulus to very rapid 
growth and division in the cells of the venter as well as in those of the thallus 
immediately below (figs. 14-17, PI. XVI). This results in the early for¬ 
mation of a massive “calyptra,” of which only the upper portion has been 
derived from the archegonium (figs. 17, 18; see also MacVicar, 1912, p. 
50, fig. 1). The cells of the thallus in close proximity to the young embryo 
contain a large number of chloroplasts and are doubtless active in metab¬ 
olism. As observed by Miss Clapp, rhizoids arise from the basal portion 
of the “calyptra” and probably help to supply water and mineral nutrients 
for the increased metabolic activity. 
According to Miss Clapp, the first segmentation of the fertilized egg 
is tranverse and divides the zygote into a hypobasal cell, which elongates 
into a haustorium, and an epibasal cell which gives rise to the embryo proper. 
Only three two-celled embryos have been found in my preparations, and 
none of these appears to have been alive or growing when fixed. The one 
shown in figure 41, Plate XIX, was sectioned obliquely, but it is obvious 
that it was in a degenerating condition; it had not elongated, the cytoplasm 
of the cells shows no definite organization, and all the protoplasmic content 
has disappeared from the cells of the wall of the archegonium. Figure 14, 
Plate XVI, shows another two-celled embryo whose haustorium is fairly 
well developed, but whose epibasal cell had apparently begun to disinte¬ 
grate; the nucleus is scarcely recognizable, and the cytoplasm is disorganized. 
The third two-celled embryo, not figured, is intermediate between these 
two, both as to the amount of elongation and as to the degree of preservation 
of its protoplasmic content. 
The youngest apparently normal embryo found is shown in figure 15, 
Plate XVI; it consists of three cells, a haustorium of one cell and the em¬ 
bryo proper of two cells. In this case the division of the epibasal cell was 
in a plane at right angles to the first division of the zygote. Figure 16 rep¬ 
resents a longitudinal section of a nine-celled embyro; the embryo proper 
consists of a regular octant, of which two cells adjacent to the haustorium 
are in telophase. Figure 17 shows a later stage, in which the haustorium 
has reached its full size and in which the capsule can be distinguished from 
the seta. Figure 18 shows in outline the mature sporophyte within the 
massive “calyptra.” 
Miss Clapp describes the first three divisions in the zygote as horizontal, 
resulting in the formation of a filament of four cells, including the haus- 
