]0 2 M use IN EM. 



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 Anthoceros form at first two, and afterwards four, new nuclei 

 (in addition to the primary nucleus), which are arranged tetrahedrally ; the 

 division-walls advance from without inwards, by which means the spherical mother- 

 cell breaks up into four spores. In Pellia and Frullania, on the other hand, the 

 division of the mother-cells commences by four protuberances arranged tetra- 

 hedrally, which at length separate by constriction ; each contains a nucleus, and 

 they form as many spores ; in Pellia the spores immediately again divide several 

 times, and thus give rise to the sexual generation. 



Fig. -zit.— Anthoceros Icmis (after Hofmeister); A a branched thallus ; B longitudinal section of a shoot (X40); an 

 antheridia beneath the layer of superficial cells ; C longitudinal section through the apical part of a shoot ; ar rudiments of 

 archegonia (X500) ; D ar fertilised archegonium in the longitudinal section of a shoot, with rudimentary sporogonium 

 consisting of two cells ; E multicellular rudimentary sporogonium ; A' in 5 a colony of Nostoc settled in the tissue of 

 the thallus. 



The Hepaticse are usually divided into five families, viz. : — 



1. Anthoceroteae, 



2. Ricciese, 



3. Monocleae, 



4. Marchantieae, 



5. Jungermanniece, 



of which the first four include only thalloid forms, the fifth both thalloid and foliose 

 genera. 



I. Anthocerotese. Anthoceros IcB'vis 2L\\d punctatus, 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, 

 and the apical cells of the branches which lie in the anterior depressions are divided 

 by walls inclined alternately upwards and downiwards (Fig. 216, C). In each of the 

 cells of the thallus, the upper layer of which does not become differentiated into an 

 epidermis, only one mass of chlorophyll is formed, surrounding the nucleus. On the 

 under side of the thallus, Janczewski states that stomata are formed close behind the 



