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 adjacint 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 eff^ect from a single 

 trichogyne to numerous carpogonial branches, and thus one act of fertilisation suffices 

 for the developement of several cystocarps on diiferent branches^. 



C. The Charace^^^ 



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 tV 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 rotwidns, also 

 by Berthold in Halymenia Floresia and nlvoidea, Nemastoma dichotonia and cervicornis, Grateloupia 

 Consentinii, Jilicina, and dichotoma, and by Sclimitz in the Squamariej.e : see Falkenberg, Die Algen, 

 1881.] 



^ A. Braun, Ueber die Richtungsverhaltnisse der Saftstrome in den Zellen der Charen, in Monats- 

 berichte der Berliner Akad. der Wiss. 1852 and 1853. — Pringsheim, Ueber die nacktfussigen Vorkeime 

 der Charen, in Jahrb. f. wissen. Bot. 1864, vol. III. — Nageli Die Rotationsstromung der Charen, in 

 his Beitragen zur wissen. Bot. i860, vol. II. p. 61. — Thuret, Sur les antheridies des cryptogames, 

 Ann. des Sci. Nat. 1851, vol. XVI. p. 19. — Montague, Multiplication des charagnes par division, 

 ditto, 1852, vol. XVIII. p. 65.— Goppert u. Cohn, Ueber die Rotation in Nitella Jiexilis, Bot. Zeitg. 

 1849. — De Bary, Ueber die Befruchtung der Charen, Monatsber. der Berliner Akad. May 1871. 

 [For additional Bibliography, see Lindley, Vegetable Kingdom, 3rd edit. p. 28 : also Journal of 

 Botany, 1878.] 



