Asexual Reproduction in Hepaticae. 125 
of the young plant, air-spaces are formed, whilst the cells towards 
the ventral surface remain in close contact with each other, and the 
large superficial cells mentioned grow out to form rhizoids. The 
germination of the gemmae has been carefully studied by Pfeffer, 
Zimmennann, 1 and Benecke. 2 
II. pf anger mamiiales. A. yungermanniaceae Anacrogynae. 
In the thalloid forms belonging to this series, vegetative repro¬ 
duction takes place by the same methods as in the majority of the 
Marchantiales, namely, the separation of the younger branches by 
the dying away of the older parts of the thallus, and the production 
of caducous adventive branches. When gemmae are developed, these 
are usually much simpler in structure than in the Marchantiales. 
Fam. 1. Sphaerocarpoideae. In Sphaerocarpus, adventive 
branches are frequently formed from various parts of the thallus, 
arising from the superficial cells and ultimately falling away and 
growing independently. The tubers of Geothallus tuberosus, an 
interesting Californian liverwort described by Campbell, 3 may be 
mentioned here, though their function appears to be rather that of 
enabling the plant to persist during seasons of drought rather than 
that of bringing about asexual multiplication of the plants. The 
tuber is formed immediately behind the growing-point of the shoot, 
its tissue consists of cells with dense proteid contents, and it 
remains alive after the rest of the plant has become withered up. 
The growing-point at the anterior end of the tuber ultimately 
resumes its activity and gives rise to a new shoot. 
Fam. 2. Metzgerioideae. Most of the species of Aneura and 
Metzgeria are distinguished by the frequent formation of adventive 
branches which become detached and form new plants. 4 In Aneura, 
these branches are usually formed at the margins of the thallus; in 
Metzgeria , they arise chiefly from the lower surface of the mid-rib, but 
may spring from any part of the thallus, on either the upper or the 
lower surface. Each of these branches is developed from a single 
cell; this cell projects from the surface and becomes divided by 
intersecting walls, cutting out a wedge-shaped (“two-sided”) cell, 
which forms the apical cell of the new shoot. 
1 Zimiuermaun, A., Ueber die Einwirkung des Liclites auf 
dem Marchantieenthallus. Arb. desbotan. Inst., Wurzburg, 
Band 2. 
2 Benecke, W., Ueber die Keiuiuug der Brutknospen von 
Lunularia cmciatn. Botan. Zeitung, 1903, Abt. 1, p. 20. 
3 Campbell, D. II., The Development of Geothallus tuberosus. 
Annals of Botany, Vol. 10, 1896, pp. 491-510. 
Goebel, K, Ruckschlagsbildungen und Sprossung bei 
Metzgeria. Flora, 1898, p. 69. 
4 
