=365. Structure of the conceptacles.=—On making sections of the fruiting portions one finds the walls of the cavities covered with outgrowths. Some of these are short branches which bear a large rounded terminal sac, the oogonium, at maturity containing eight egg-cells. More slender and much-branched threads bear narrowly oval antheridia. In these are developed several two-ciliated spermatozoids. [Illustration: Fig. 177. Oogonium of Fucus with ripe eggs.] [Illustration: Fig. 178. Antheridia of Fucus, on branched threads.] =366. Fertilization.=—At maturity the spermatozoids and egg-cells float outside of the oval cavities, where fertilization takes place. The spermatozoid sinks into the protoplasm of the egg-cell, makes its way to the nucleus of the egg, and fuses with it as shown in fig. 181. The fertilized egg then grows into a new plant. Nearly all the brown algæ are marine. [Illustration: Fig. 179. Antheridia of Fucus with escaping spermatozoids.] [Illustration: Fig. 180. Eggs of Fucus surrounded by spermatozoids.] [Illustration: Fig. 181. Fertilization in Fucus; _fn_, female nucleus; _mn_, male nucleus; _n_, nucleolus. In the left figure the male nucleus is shown moving down through the cytoplasm of the egg; in the remaining figures the cytoplasm of the egg is omitted. (After Strasburger.)] =367. The Gulf weed= (=Sargassum bacciferum=) in the warmer Atlantic ocean unites in great masses which float on the water, whence comes the name “Sargassum Sea.” The Sargassum grows on the coast where it is attached to the rocks, but the beating of the waves breaks many specimens loose and these float out into the more quiet waters, where they continue to grow and multiply vegetatively. =368. Uses.=—Laminaria japonica and L. angustata are used as food by the Chinese and Japanese. Some species of the Laminariaceæ are used as food for cattle and are also used for fertilizers, while L. digitata is sometimes employed in surgery. _Classification._—Kjellman divides the Phæophyceæ into two orders. =369. Order Phæosporales (Phæosporeæ)= including 18 families. One of the most conspicuous families is the Laminariaceæ, including among others the Giant Kelps mentioned above (Laminaria, Postelsia, Macrocystis, etc.). =370. Order Cyclosporales (Cyclosporeæ).=—This includes one family, the _Fucaceæ_ with Ectocarpus, Sphacelaria, Læathesia, Fucus, Sargassum, etc. Class Rhodophyceæ. =371. The red algæ (Rhodophyceæ).=—The larger number of the so-called red algæ occur in salt water, though a few genera occur in fresh water. The plants possess chlorophyll, but it is usually obscured by a reddish or purple pigment. =372. Nemalion.=—This is one of the lower marine forms, though its thallus is not one of the simplest in structure. The plant body consists of a slender cylindrical branched shoot, sometimes very profusely branched. The central strand is rather firm, while the cortex is composed of rather loose filaments. [Illustration: Fig. 182.