Sphcerocarpales. 85 
point with an apical cell from which segments are cut off above 
and below, as well as laterally. The thallus consists almost 
entirely of uniform green cells, arranged in several layers at the 
middle, where it is attached to the soil by rhizoids, and thinning 
out to a single layer at the margins. At the growing points, there 
are, especially on the underside, mucilage-hairs consisting of a row 
of cells, the terminal cell being large and club-shaped. Petounnikow 
(25), who, in 1867, discovered the male plants of Sphcerocarpus, 
regarded these hairs as rudimentary leaves, corresponding to the 
A 
Fig. 1. Diagrams illustrating the early development of the Antheridium 
in Marchantiales (upper row), Sphcerocarpales (lower row, right), and 
Jungermanniales (lower row, left) ; cross-sections shown in C and E of upper 
series, and in C and D of lower series. 
ventral scales of the Marchantiales and the amphigastria or under¬ 
leaves of the Acrogynae, and there is abundant evidence for the 
