292 
THALLOPHYTES. 
investment, which subsequently opens at the apex. The trichogyne and the trichophore 
can be observed lying externally to it (Fig. 190, tg). It is evident from these examples 
that neither the trichogyne nor even the cells of the trichophore undergo any further 
development as a consequence of fertilisation, but that it is in cells adjacent to them that 
the consequences of fertilisation are manifested, in their growth, branching, division, and 
final formation of spores. The formation of an investment is also a consequence of 
fertilisation. The fruits of Florideae are usually termed Cystocarps. 
(3) The most complicated and most extraordinary process of fertilisation was found 
to occur by Thuret and Bornet in the genus Dudresnaya. Here the cystocarps are 
formed upon branches other than those which bear the trichophore. After that the 
long trichogyne, which is coiled at its base, has been fertilised, tubular branches spring 
from beneath it, which grow towards the true fertile carpogonial branches. Each of 
these latter has a spherical apical cell to which the outgrowth from the trichophore applies 
itself, and at the point of contact the cell-walls become absorbed. The apical cell of the 
carpogonial branch which has thus been fertilised becomes distended and filled with 
protoplasm ; it becomes isolated by the formation of cell-walls, and then gives rise to the 
cystocarp. These tubular outgrowths convey the fertilising effect from a single 
trichogyne to numerous carpogonial branches, and thus one "act of fertilisation suffices 
for the developement of several cystocarps on different branches^. 
C. The CHARACEiE^. 
The carpogonium consists of one relatively large cell and several smaller ones. The 
latter are known as ' Wendungszellen,' and probably represent a very rudimentary 
trichophore, the trichogyne of which is undeveloped. Fertilisation is effected by means 
of filiform antherozoids which are formed in very remarkable antheridia. The carpogo- 
nium is invested before fertilisation by five spirally-wound cells which arise from its 
stalk-cell. As a consequence of fertilisation the large cell of the carpogonium becomes 
a resting spore, producing, by its germination, a pro-embryo from which the sexual 
plant springs as a lateral shoot. No gonidia are formed. 
The Gharaceae are submerged aquatic plants, rooting in the ground and growing 
erect, attaining a height of from iV metre to a metre, and containing abundance 
of chlorophyll. They are very slender, forming stems and leaves only § to 2 mm. 
in thickness. With an alga-like habit, they possess a delicate structure, though some- 
times attaining greater firmness from the deposition of lime on their surface. They 
live gregariously, mostly in crowded tufts, at the bottom of fresh-water ponds, ditches, 
and streams; they may grow in deep or in shallow, in stagnant or in quickly-flowing 
water ; and are either annual or perennial. 
In the greater number of species, which are distributed over all quarters of the 
globe, there prevails nevertheless so great a uniformity that they may all be arranged 
into two genera. 
' [This mode of fertilisation has been detected by Thuret and Bornet in Polyides rohindns, also 
by Berthold in Halymenia Floresia and luvoidea, Nemaslotna dichotojna and cervicornis, Grateloupia 
Cotisefitifiii, filicina, and dichotoma, and by Schmitz in the Squamarie&e : see Falkenberg, Die Algen, 
1881.] 
^ A. Braun, Ueber die Richtungsverhältnisse der Saftströme in den Zellen der Charen, in Monats- 
berichte der Berliner Akad. der Wiss. 1852 and 1853. — Pringsheim, Ueber die nacktfüssigen Vorkeime 
der Charen, in Jahrb. f. wissen. Bot. 1864, vol. III. — Nägeli Die Rotationsströmung der Charen, in 
his Beiträgen zur wissen. Bot i860, vol. II. p. 61. — Thuret, Sur les antheridies des cryptogames, 
Ann. des Sei. Nat. 1851, vol. XVI. p. 19. — Montagne, Multiplication des charagnes par division, 
ditto, 1852, vol. XVIII. p. 65. — Göppert u. Cohn, Ueber die Rotation in Nitella flexilis. Bot. Zeitg. 
1849. — De Bary, Ueber die Befruchtung der Charen, Monatsber. der Berhner Akad. May 1871. 
[For additional Bibliography, see Lindley, Vegetable Kingdom, 3rd edit. p. 28 : also Journal of 
Botany, 1878.] • 
