11 
A Fountain Alga. 
spread out all over the coverslip, thus bathing equally all parts of 
it. The suction produced inside the cell kept the coverslip firmly 
in position, and obviated the employment of any vaseline. By 
this means the growth of the Alga could be followed from day to 
day and its life-history made out, without the coverslip being 
removed. 
This life history is most easily traced from the zoospores, 
which were discovered to be readily formed under the conditions 
above described. 
The germinating zoospore (Plate 1, Fig. 1) gives rise to a short 
filament, which by lateral budding grows into an irregularly 
branched thallus of a star-shaped or circular form with filamentous 
branches joined laterally to one another to form a compact disc, all 
radiating out from a common centre (Figs. 5, 6, 7). 
The thallus is flattened and closely appressed to the substratum, 
to which it is firmly fixed, and even a very strong fine stream of 
water directed straight on the thallus fails to dislodge it or cause 
any displacement. 
It is at first but one cell thick, and although it may be subse 
quently thicker, it never forms erect outgrowths or branches. 
The first division wall of the germinating zoospore is at right 
angles to the long axis of the young filament, but lateral buds may 
arise before any division walls are seen (Fig. 2). The empty case 
from which the filament grew may be seen for about seven or eight 
days after germination, but eventually disappears (Figs. 1, 2, 3). 
The individual cells are longer than broad, and the long axis is 
coincident with the axis of the filament. 
The tip of a filament is rounded, and not swollen or pointed. 
The chloroplast is a parietal plate extending all round the 
internal wall of the cell and is of a bright green colour. There are 
no visible pyrenoids. 
In about a month’s time the germinating zoospore has grown 
into a more or less star-shaped thallus (Fig. 6) at present but one 
cell thick, the filaments of which are composed of cells much 
longer than broad. 
About this time one or two cells in the centre of the thallus 
may be seen to be differentiated from the other cells (Fig. 7). 
•Their walls become thicker, darker and more easily seen, and the 
chloroplasts, hitherto parietal, become fragmentary and scattered 
all over the cell. The colour of these cells also becomes much 
darker, forming a striking contrast to the lighter green of the 
