MARINE ALG^. 



273 



united in a bunch as in Griffithsia, or enclosed in a trans- 

 parent cylinder, as in Polysiphonia, or covering a kind of ex- 

 panded disc of peculiar form, as in Laurencia.'^ According 

 to competent observers, these cellules contain spermatozoids. 

 Nageli describes the spermatozoid as a spiral fibre, which, as 

 it escapes, lengthens itself in the form of a screw. Thuret 

 does not coincide in this view ; on the contrary, he says 

 that the contents are granular, and offer no trace of a 

 spiral filament, but are expelled from the cells by a slow 

 motion. The antheridia appear in their most simple form 

 in Gallithamnion, being reduced to a mass of ceils com- 

 posed of numerous little bunches which are sessile on the 

 bifurcations of the terminal branches. Are not these spiral 

 filaments closely allied to Oscillator iacece .? The spores are 

 simpler structures than the tetraspores, and mostly occupy 

 a more important posi- 

 tion. They are not scat- 

 tered through the frond, 

 but grouped in definite 

 masses, and generally 

 enclosed in a special 

 capsule or conceptacle, 

 which may be mistaken 

 for a tetraspore case. 

 The simplest form of 

 the spore fruit consists 

 of spherical masses of 

 spores attached to the 

 wall of the frond, or 

 imbedded in its sub- 

 stance, without a prope" 

 conceptacle ; such a fruit 

 is called a favellidium, 

 and occurs in Raly- 

 menia ; the same name 

 is applied to the fruits 

 of similar structures not 

 perfectly immersed, . as 

 those of Gigartina^ Gelidium, &c., where they form tuber- 

 cular swellings on the lobes. In some, the tubercles pre- 

 sent a pore at the summit, through which the spores find 



Fig. 150.— Ciitleria dichotoma. Section of a 

 lacinia of a frond, showing the stalked eight 

 chcunbered oosporangcs igroxuing on tufts 

 with intercalated hairs. Magnified 50 dia- 

 meters. 



