Wolfe . — Cytological Studies on Nemcilion. 613 
transient and entirely independent of nuclear activity in rapidly growing 
cells. 
Although this is the normal process of chromatophore division, in 
exceptional cases it seems to take place in a different manner ; a new 
chromatophore being organized from one of the coarser strands of the 
other. This condition, which was described by Schmitz (’ 82 ), and has 
been seen by the writer, may perhaps account for the not infrequent 
presence of two chromatophores in old cells. 
This body is constantly present in all phases of the life history of the 
plant, and in all cases arises from a pre-existing body of the same nature. 
The fact that in sperm-cells it disappears in a manner that will be hereafter 
described, and that, for a short time after the second division of the zygote, 
it has been impossible to demonstrate it, owing no doubt to the dense sur- 
rounding cytoplasm, does not militate against the accuracy of this statement. 
Maturation and Sexual Reproduction. 
Oogenesis. 
The carpogonium, as is well known, is borne at the end of a short 
branch, developed in connexion with sterile branchlets at right angles to 
the longitudinal axis of the frond. This carpogenic branch is composed 
usually of three cells ; since, however, the number varies from two, in the 
simplest noted, to as many as five, it cannot be considered as in any way 
significant. It can be readily recognized even when, as in its youngest 
stage, it consists of but a single cell. Its peculiar shape (Fig. 1), as well 
as its capacity for absorbing dyes, serves to differentiate it at once in 
stained preparations. In life its almost colourless condition renders it 
equally conspicuous. The members of this branch arise by the divisions 
of the primary carpogonial cell, which acts as an apical cell by cutting off 
successive basal segments. 
The cells of the branch, excepting in shape and colour, are organized 
practically just as are the ordinary thallus-cells (Fig. 2). Janczewski 
(’ 76 ) describes the cells of which it is composed as being without nuclei and 
chromatophores ; a manifestly erroneous statement, since there is present 
a well-defined nucleus differing in no way from the usual type. The chro- 
matophore is not conspicuous in the living cell, because of the small amount 
of pigment which it contains, but staining brings it out readily. In some 
cases, at least, a distinctly appreciable amount of colour is present even in 
the living condition. The cells are short cylindrical blocks contrasting 
rather sharply in form with the usually ellipsoid cells, which are character- 
istic of vegetative filaments (Fig. 24). The lowest cell of the series par- 
takes to some extent of the characters of both, and thus lessens the 
abruptness of the transition between the two types. 
As the carpogenic branch becomes differentiated its terminal cell 
