S lurch. — Harvey ell a mirabilis ( Schmitz & Rein he). 93 
with Hoffmann’s blue, the upper cell staining more deeply 
than the lower. This lower large cell, which includes also 
the two small filaments, undergoes no further change. The 
upper cell rapidly divides (Fig. 15) and gives rise to the 
young gonimoblast (Fig. 16). The gonimoblast branches 
copiously and ramifies horizontally in all directions among 
the cells of the thallus (Figs. 3 and 17). From the cells of 
these horizontal filaments arise numerous much-branched 
tufts of erect gonimoblast-filaments, which eventually bear 
the spores (Fig. 17). At about the time of the commence- 
ment of the development of the gonimoblast, the ordinary 
thallus-cells which are situated at the base of the peripheral 
layer, at about the same level as and near to the auxiliary 
cell, commence to elongate. It may be mentioned that just 
after fusion with the carpogonium, the auxiliary cell becomes 
connected with some of the thallus-cells near it (Fig. 15), and 
that these are the first ordinary thallus-cells to elongate. 
As the gonimoblast develops, these cells become more and 
more elongated, carrying up the peripheral layer with them. 
Those thallus-cells which are in immediate proximity to the 
fertilized auxiliary cell commence to elongate first ; and as 
the gonimoblast develops further, so the thallus-cells, at about 
the same level, and among which it is forcing its way, also 
become elongated. Hence the elongation of ordinary vege- 
tative cells, carrying up the peripheral layer, and thus providing 
space for the development of the erect gonimoblast-filaments 
which bear the spores, accompanies the development of the 
gonimoblast from its commencement. These lengthened 
cells are shown in the mature cystocarpic plant in Fig. 17. 
It may be noted that the peripheral cells in the mature 
cystocarpic plant are smaller and more circular in outline 
than in younger fronds. 
The erect gonimoblast-filaments arise from the cells of the 
horizontal filaments of the gonimoblast. They form erect, much 
branched, often spreading tufts, which develop in the spaces 
between the elongated thallus-cells supporting the peripheral 
layer (Fig. 17). The cells of these erect filaments are usually 
