The result of this impregnation is seen 
sometimes at the base of the trichogyne 
We “at ene Sy ek oe. Be oh hal wi *' Po ae? « < ade ey! aaa * 
te 1 ESCO a ar eae, A ie SAY Dy’ { é 
* rT) + ie 54, —— 7 . ~) = 
. ? A ahecs ‘ ‘ 4, - : Pa eo’ 
o* wy Me | " - eee gia : ‘ + ? 7 
bs at “he , ar? 7 i \ ri ‘ {* xP wv ; \ oer net, a P 4 ~ fs J a ‘ 
a Sait eS -e < \ 4 r B , ‘ , ‘ i 4 
ing 
Special Morphology and Classification.  — 253 
through a slit and forces itself into the oogonium through an 
opening formed at the same time in its cell-wall, and finally 
reaches the oosphere, which then developes into a resting- 
spore. In the Florideze the antherozoids — 
® 
[are unprovided with cilia and] are only : i" 
moved about passively in the water; they 
attach themselves to a hair-like cell, the. Pe: % 
trichogyne, emptying their contents into it. Ch 
(in WVemalium, Fig. 386), sometimes in i: ee 
adjoining cells (in the Ceramiacez), some- ae 
‘times (in Dudresnaya) in altogether dif- : oe 
ferent branches, on which cystocarfs are at 
formed, which contain the oospores. : | a) 
In many sections of Algz different : ie 
modes of reproduction occur in the same 
species; and these are often associated 
into an Alternation of Generations ; by 
which is meant that the mode of repro- 
duction varies according to the genera- 
tion. This occurs especially in the fresh- 
water Algze, where an individual which is 
developed out of a swarmspore itself pro- 
Fic. 386.—Fertilisation 
duces sexual organs, and wice versa. of Nemala7e oe 
tifidum; the globular 
Alge are submerged water plants, or antherozoidsat the apex 
: j of the trichogyne. 
at all events require water for their pro- 
cesses of development, and especially for their reproduc- 
tion. Certain vital phenomena, as for instance the alter- 
nation of generations and the production of swarmspores, are 
sometimes dependent on immersion in water following 
the drying-up of the cells. The degree of concentration 
of the fluid in which Alge grow has also a great influ- 
ence on their development. Chlorococcus infusionum, for 
example, propagates itsclf in a less dense nutrient fluid 
by means of swarmspores, in a more concentrated meé-— 
