= 
CELL-DIVISION.—REJUVENESCENCE.—CONJUGATION. [777 
takes place in the formation of pollen cells has already been 
described at page 258 of this volume. The manner in which 
spores are formed in the higher Flowerless Plants is substan- 
tially the same in most cases. It sometimes happens, however, 
that in the developmentof pollen and spores, the special parent 
cells are nut formed, as has been shown by Schacht in the 
pollen of Gnothera and 
in the spores of Aitho- Fic. 1135. 
ceros levis ; and by Hen- 
frey in the spores of 
Marchantia polymorpha 
(fig. 1133). 
In other cases, in- 
stead of the development 
of only four secondary 
cells in the cavity of the 
parent, the whole mass 
of the protoplasm may 
break up into a great 
number of small parti- 
cles, as in the production 
of the swarm-spores of 
many Algze and Fungi 
( fig. 1134). In this case 
the new cells (primor- 
dial) are only clothed 
by a cellulose wall after 
their separation from the 
parent- or mother-cell. 
The formation of the 
oospheres in Achlya (fig. 
1135), is a modification Fis. ae Peers ee eee of Achlya ligni- 
° ea cola, showing cell-division. e letters A to E 
of this prerens of divi indicate the course of development. The proto- 
sion. Some of these plasm of a cell or branch of a cell collects into 
modifications of cell- a globular form A, B, and by the formation of a 
acini 1] l septum, D g, becomes an independent cell (the 
1vis10nN are ClOS€ly aNa- = gogonium) in which nucleus-like bodies may 
logous to the ordinary appear, Cc. The protoplasm then breaks up into 
process of free cell-for- SN iuny become spherical, anvdafter fertilisation 
mation to which by by the antheridia a, A, penetrating into the 
many authors they are  Sosyniin, by then sus ba een ree 
referred. Sachs.) 
c. Rejuvenescence.— 
Another method of cell-division is that which is termed reju- 
wenescence or renewal of a cell, where the whole contents of a 
cell contracts, some of the cell-sap is expelled, the chlorophyll 
becomes rearranged, and its whole form alters as it escapes from 
the cell-wall and eventually forms a fresh cell-wall. This process 
may be well seen in the swarm-spores of (Hdogonium (fig. 1136). 
d. Conjugation.—The production of azygospore, which occurs 
