35^ 
MUSCINEJE. 
in this manner attained its destined height, and partially even at an earlier period, 
a number of divisions of different kinds take place by which the structure is com- 
pleted. The wall of the sporogonium becomes differentiated from the tissue from 
which the mother-cells of the spores are to arise ; if elaters are formed they originate 
from the same tissue, the cells ceasing to divide transversely at an earlier period 
and remaining long, while the intermediate cells become rounded off and give 
rise to the mother-cells of the spores (Hofmeister). 
The mode of division into four of the mother-cells of the spores also 
varies. Those of Anihoceros form at first two, and afterwards four, new nuclei 
which are arranged tetrahedrally, the protoplasm dividing before the nucleus ; cell- 
walls are then formed, and thus the mother-cell breaks up into four spores ^ In 
Pellia and Frullam'a, on the other hand, the division of the mother-cells commences 
by four protuberances arranged tetrahedrally, which at length are cut off by cell- 
walls; each contains a nucleus, and they form as many spores; in Pellia the spores 
immediately again divide several times, and thus give rise to a young plant. 
The Hepaticse are usualy divided into five families, viz.: — 
1. Anthoceroteae, 
2. Riccieae, 
3. Monocleae, 
4. Marchantieae, 
5. Jungermanniese, 
of which the first four include only thalloid forms, the fifth both thalloid and foliose 
genera. 
I. AnthoceroteaB. Anthoceros la'vis a.nd punctafuj, which grow in summer on loamy 
ground, develope a perfectly leafless flat ribbon-like thallus, its irregularly developed 
ramifications forming a circular disc ; the regularity of the dichotomous branching is 
disturbed by the adventitious shoots, which proceed from the margin of the thallus, and, 
in A. punctatus, also from the upper surface. The thallus consists of several layers of 
cells, and the apical cells of the branches which lie in the anterior depressions are 
divided by walls inclined alternately upwards and downwards (Fig. 237, C). In each 
of the cells of the thallus, the upper layer of which does not become diflferentiated 
into an epidermis, only one chlorophyll-granule is formed, surrounding the nucleus. 
On the under side of the thallus, Janczewski states that stomata are formed close behind 
the growing margin, through which filaments of Nostoc frequently penetrate, forming 
roundish balls in the tissue of the thallus (Fig. 237, B), which were at one time considered 
to be endogenous gemmae^. The antheridia and archegonia arise apparently without 
any definite arrangement in the interior of the upper side of the thallus. The formation 
of the antheridia commences by a circular group of cells of the outer layer separating 
from the subjacent tissue and thus producing a broad intercellular space, several of the 
lower bounding cells of which, after some vertical divisions, rise up in the form of 
papillae, and form the antheridia (Fig. 237, B, an). It is only when the chlorophyll- 
granules in the walls of the antheridia have assumed a yellow colour and the anther- 
ozoids are mature that the roof of the cavity is ruptured, the antheridia opening 
at their apex and allowing the antherozoids to escape. In the Riccieae and Mar- 
chantieae the archegonia, which are at first free, become gradually surrounded by masses 
of tissue, but in Anthoceros they are enclosed from the first. One of the superior 
^ [On the development of the spores of Pellia and Anthoceros see Strasburger, Zellbiidung und 
Zelltheilung, 3vd ed. p. 156.] 
2 [See Waldner, Ueb. die iVos^oc-Colonieen bei Blasia, Sitzber. d. Wien. Akad. 1878.] 
