1918] HAUPT—PALLAVICINIA 529 
calary divisions, much in excess of the young sporophyte. The 
perianth keeps pace with the elongation of the embryo, reaching a 
maximum height of about 5 mm. At the time immediately pre- 
ceding spore disperal, the seta shows remarkable growth, becoming 
25-27 mm. long. The perianth attains a thickness of 3 or 4 cells, 
as seen in cross-section, and becomes fringed around the top. The 
involucre, on the other hand, does not at any time exceed the height 
of the archegonia and it is related to their protection in the same 
way that the perianth is associated with the protection of the sporo- 
phyte. With the development of the perianth, following fertiliza- 
tion, the involucre becomes flaring and denticulate around the top. 
After fertilization the egg cytoplasm becomes denser and a 
heavy wall is laid down around the protoplast, thus making it 
independent of the tissue of the archegonium. 
Sporophyte 
The youngest sporophyte which was observed consisted of a tier 
of 4 cells (fig. 26). The first division is followed by a transverse 
wall in the lower segment and then by a similar wall in the upper 
segment. A vertical division then occurs in the upper half of the 
embryo (figs. 27, 28), followed by vertical and transverse walls. 
The lower half of the embryo usually undergoes one vertical divi- 
sion, but contributes nothing to the development of the foot, seta, 
or capsule (fig. 29). Half of the potentially sporogenous tissue 
derived from the fertilized egg thus is diverted for haustorial pur- 
poses. A similar situation has been observed by Miss Ciapp (3) 
in Aneura pinguis, and by CAMPBELL and WILLIAMs in Pallavicinia 
Zollengeri. The relation between the early divisions in the embryo 
and the development of the 3 regions of the sporophyte could not 
be ascertained, material being wanting. The differentiation of the 
sporogenous tissue, however, occurs relatively late. According to 
FARMER (4), the young embryo of Pallavicinia decipiens consists of 
a tier of 3 cells, the upper segment forming the capsule, the middle 
segment the seta and part of the foot, and the lower segment the 
rest of the foot. 
With the growth of the embryo, the venter of the archegonium 
becomes a calyptra 4 or 5 cells in thickness, which grows in length 
