F. Cavers. 
162 
divided repeatedly by transverse walls, giving rise to a row of cells. 
The uppermost cell then became enlarged and divided by a 
longitudinal wall. Repeated transverse and longitudinal divisions 
then occurred in this swollen terminal portion, in the interior of 
which an intercellular space was formed by splitting of the primary 
longitudinal wall. This closed sac then became filled with mucilage? 
whilst two other mucilage-cavities were also formed immediately 
above the insertion of the stalk of the gemma, but each of these 
opened externally by a slit and resembled the ordinary Nostoc- 
cavities of the thallus. The tubers which have been described in 
various exotic species of Anthocevos , and more recently by Goebel 1 
in A. laevis itself, may be regarded as organs of asexual propa¬ 
gation, especially when several tubers are borne on one plant. 
These tubers, as in the case of Riccia, Fossombronia, Geothallus , and 
Petalophyllum , arise as swellings on the lower surface of the thallus, 
near the margin; their cells contain reserve food-materials, and 
they are adapted for carrying the plant over unfavourable climatic 
periods and of germinating to form new plants. 
Regeneration of the Gametophyte. 
Necker appears to have been the first to describe the process 
of gametophytic regeneration in Hepaticae. In his “ Physiologia 
Muscorum,” published in 1774, he states (p. 27) that he cut the 
thallus of Marchantia polymorpha and of Fegatella conica into 
numerous small pieces, which he cultivated on soil and watered 
daily. In about a month, he observed outgrowths arising from 
many of the fragments, each outgrowth at length giving rise to a 
new plant. He obtained similar results in his experiments wijth 
Ricciella jluitans and with a number of leafy Jungermanniales 
These observations of Necker’s appear to have been entirely over¬ 
looked by later writers on the subject. 
In 1885 Vochting 2 published an important paper in which he 
showed that the gametophyte of Lunnlaria and Marchantia 
possesses in an extraordinary degree the property of regeneration. 
On cutting out portions of the thallus or of the sexual receptacles 
and keeping them under cultivation, he obtained numerous adventive 
outgrowths, each arising from a single cell. Even when portions of 
the thallus were minced up into very small fragments, many of the 
latter were found to give rise to new shoots. Vochting therefore 
concluded that in the gametophyte of these Liverworts, every cell 
1 Goebel, K., Organograpliie der Pflanzen, p. 294. 
2 Vochting, II., Ueber die Regeneration der Marchantieen. 
Jahrb. fur wiss. Botauik, Band 16, Heft 3, 1885. 
