86 
F. Cavers. 
view that leaves have arisen, in various groups of Liverworts, from 
mucilage-hairs primarily adapted for protection of the growing 
apex. Campbell (4) discovered in plants of 6. californicus, growing in 
unusually moist and shaded places, regular marginal lobes or leaves 
comparable with those of Blasia or Fossombronia. 
The genus is dioecious, the male plants being extremely small, 
(usually little more than 0*1 mm. in diameter) and often covered by 
the larger female plants. The development of the antheridium is 
interesting, since it forms a type intermediate between those 
observed in the Marchantiales and the Jungermanniales (Fig. 1.) 
The mother-cell divides transversely ; the basal cell undergoes no 
further division, but the upper divides to form three superposed 
cells ; of these the lowest divides again to form the short stalk, 
while vertical walls appear in the two upper cells, giving an octant 
stage. In each of the eight cells a periclinal wall is then formed, 
cutting off a wall-cell from a primary sperm-cell. The body of the 
ripe antheridium is spherical. The surrounding cells of the thallus 
grow out to form an envelope which extends far beyond the 
antheridium itself and becomes flask-shaped (Fig. 2 ,a). 
Fig. 2. Sphesrocarpus terrestris. A, a male plant, x 40 ; 13, a female plant, x 10. 
The archegonium show's the typical Liverwort development, 
fully described by Campbell (3). When mature, it is sessile, and 
its neck consists of six rows of cells, with an axial row of four 
canal cells; it should be noted that the archegonium of the 
Sphaerocarpales exactly resembles that of the Marchantiales, 
whereas in Jungermanniales there is usually a stalk and there 
are five rows of neck cells. The neck is strongly curved forwards, 
as is the envelope which grows up around the archegonium (Fig. 2, B). 
The envelope develops independently of fertilisation, and loosely 
