STRUCTURE AND DEVELOPMENT OF DENDROCEROS. 471 
two cover-cells are formed. When the archegonium is ripe, its 
apex is raised slightly above the general level of the thallus. 
If we compare the archegonium of Dendroceros with that of 
Notothylas and Anthoceros, it is found to be to a certain extent 
intermediate in character. The primary axial cell is broader than 
that of the latter, but not so broad as that of Notothylas, and the 
same is true of the primary neck-canal-cell. 
As in the other genera, the egg-cell does not fill the cavity of 
the venter. At maturity the archegonium opens and the cover- 
cells of the neck are usually thrown off, while the cells below 
them diverge more or less. 
The Antheridium. 
The antheridium of Dendroceros differs a good deal from that 
of the other Anthocerotacez, being much larger, solitary, and 
having a long pedicel, while in most species of Anthoceros and 
Notothylas the antheridia are short-stalked and occur in groups 
formed from the division of a common mother-cell. 
Owing to the very incomplete account of the antheridium 
given by Leitgeb, its development was followed with some care. 
As was shown by Hofmeister *, and later confirmed by Leitgeb 
and others, the Anthocerotacee differ from all other Hepatice 
in the endogenous origin of the antheridium. In all of them it 
arises from a sub-epidermal cell, which either develops at once 
into a single antheridium or, more commonly, divides into a 
number of cells, each of which produces an antheridium. 
In Dendroceros the antheridia are formed in strict acropetal 
succession, the youngest ones being found very near the apex. 
They are arranged in two lines, one on either side of the midrib. 
The mother-cell cannot be certainly distinguished until it 
begins to separate from the adjacent cells, when it is readily 
recognized, as the space about it is lined with a mucilaginous 
matter derived from the partially disintegrated cell-walls, which 
stains very strongly with Bismarck-brown or hematoxylin. 
The first division in the superficial cell by which the antheridial 
cell is cut off occurs in the second or third segment from the 
apex of the shoot, and the result of this division is the formation 
of two cells, an outer and an inner one, of which the latter 
becomes at once the mother-cell of the single antheridium. A 
Second transverse wall makes its appearance very early in the 
* Hofmeister, “ The Higher Cryptogamia,” Ray Soc. 1862, p. 7. 
