120 HOFMEISTER, ON 



verse expansion and subsequent repeated bipartition of 



the cells of its circumference (PI. XV, fig. 26). 



The arrangement of the spore-mother-cells and of the 

 elaters in Targionia, and also, it would seem, in the Marchan- 

 tiese, is very much the same as in Fossombronia pusilla. 

 At the time of the differentiation of the two kinds of contents 

 of the capsule, the cells destined to form the elaters are 

 hardly perceptibly longer and thinner than the future 

 mother-cells of the spores (PI. XV, fig. 29). The elaters 

 and spore-mother-cells lie across one another somewhat 

 like the chlorophyll-cells and the air-cells of the leaf of 

 Sphagnum. A remarkable longitudinal expansion of the 

 elaters first occurs when the prominences of the inner wall 

 of the spore-mother-cell begin to be seen (PI. XV, fig. 30). 



The antheridia of the Marchantiese are, as is well 

 known, united in large numbers on the upper side of pecu- 

 liarly formed shoots, and enclosed in flask-shaped cavities 

 of the tissue. 



The first stage of development of these shoots in MarcJian- 

 tia polpnorpha exactly resembles the first rudiments of the 

 head of the inflorescence. Here as there the forward, upper 

 portion of the narrow, almost cylindrical shoot becomes 

 developed considerably in breadth, protruding beyond the 

 lower, stem-like portion, like the pileus of a fungus. A 

 number of cells of the upper side of this disc, which is 

 slightly convex above and strongly so beneath, protrude 

 outwards in the form of papillae ; between them the epi- 

 dermis detaches itself from the underlying tissue. The 

 shortly cylindrical cellular processes, the first rudiments of 

 the antheridia, are outgrown by the cells surrounding them, 

 and are sunk down into circular cavities of the upper 

 surface. This arises from the rapid multiplication of the 

 cells of the circle which bears the detached fragments of the 

 epidermis, which multiplication is caused by rapid and 

 frequently repeated division of these cells by means of 

 septa parallel to the surface of the antheridial disc (PI. XV, 

 fig. 16). The above process commences in the middle 

 point of the young antheridial disc, and progresses from 

 thence to its growing margin. 



The mother-cell of the antheridium assumes the form of 



