FERTILISATION OF RED SEA-WEEDS BY ANIMALCUL&. 401 
sperm-cells of other eryptogams which are endowed with active 
cilia. From this it follows with mathematical certainty that the 
probability of the antherozoids finding thei way to the tricho- 
gynium in the presence of Vorticelle is immensely greater than 
would be the case if there were no animals present. 
At the same time it is evident that this probability is further 
~ increased in the case of Polysiphonia subulata through the presence 
of the forked hair (g h) in the vicinity of the trichogynium, because 
the whirls caused by the animalcules will often be cleft by the 
forked hair, and thus secondary whirls will be produced. Often, in 
Polysiphonia, carpogonia were found which were not fertilised. 
Thus Fig. 4 represents a ripe and spore-ejecting cystocarp (cy) 
and two carpogonia (ucg) which remained unfertilised. This was 
particularly the case on thallus-branches which were less densely 
crowded with Vorticelle—another, although negative, proof of 
Dr. Dodel-Port’s theory. It is not particularly remarkable that 
Vorticelle should inhabit Polysiphonia in large numbers, because 
these animalcules, as Dr. Dodel-Port observed, feed with predi- 
lection on the antherozoids of this plant. Thus we have here a 
condition of things similar to the relations between certain flowers 
and pollen-consuming insects. The consumption of antherozoids 
by Vorticelle is, of course, far too insignificant to merit any 
consideration, particularly if compared with the great advantages 
regarding fertilisation which the presence of the animalcule 
brings with it. Moreover, a comparison of the male plant of 
Polysiphonia with a female specimen shows that here also, as in 
most phanerogams, thousands more male cells are formed than 
are necessary for fertilisation. 
After fertilisation the carpogonium develops into a cystocarp, 
i.e., the spore-forming fruit (Fig. 4). Shortly after fertilisation 
has taken place the whole hair-apparatus disappears. The wall- 
cells of the carpogonium now begin to grow quickly and divide 
by membranes perpendicular to the surface. They form a 
cellular case (Fig. 4, h, h), which has an orifice in the apex, long 
before the spores are ripe. In the meantime the central cell 
of the fertilised carpogonium begins to form a number of densely- 
packed short branches, which, as a series of cells radiating in 
all directions, fill the basis of the capsule-shaped fruit. The 
central cell is therefore called the placenta-cell. At the 
ends of the ramified cell-series which radiate from it, pear- 
3.F 
