. Foundations of botany. did). At maturity the contents of eachdivide to form numerous very minute motile antherozoids, each withtwo delicate hairs or cilia. Dissect, by picking and by friction under cover-glass, a bunch ofantheridia and notethe branching fila-ments upon whichthey are borne. Make drawings toillustrate the variouspoints of structure. 295. Number ofAntherozoids requiredfor Fertilization.—Thebulk of an oospherehas been estimatedequal to that of thirtythousand to sixtythousand antherozoids,but apparently anoosphere may be fer-tilized by only oneantherozoid. Yet alarge number swarm
. Foundations of botany. did). At maturity the contents of eachdivide to form numerous very minute motile antherozoids, each withtwo delicate hairs or cilia. Dissect, by picking and by friction under cover-glass, a bunch ofantheridia and notethe branching fila-ments upon whichthey are borne. Make drawings toillustrate the variouspoints of structure. 295. Number ofAntherozoids requiredfor Fertilization.—Thebulk of an oospherehas been estimatedequal to that of thirtythousand to sixtythousand antherozoids,but apparently anoosphere may be fer-tilized by only oneantherozoid. Yet alarge number swarmaround each oosphereafter both haveescaped from the con-ceptacles, and oftentheir movements areso active as to cause the rotation of tlie oosphere. The process offertilization may be discerned in fresh material by squeezingoospheres and antherozoids from their respective conceptacles intoa drop of water on a slide. In some species, as Fucus platycarpus(Fig. 186), antheridia and oogonia are found in the Fig. 186. — Transverse Section of Conceptacle of aKockweed {Fucus platycarpus). (x about 35 ) Ti, hairs ; a, antheridia; o, oogonia. TYPES OF CRYPTOGAMS; THALLOPHYTES 253 THE STUDY OF :N-EMALI0N 296. Occurrence. — Seven or eight species of Nemalion are knownin the world, but only one ^ is widely diffused, being found in Europeand on the New England coast from Rhode Island northward. Itgrows in salt water attached to exposed rocks at low-water represents the largest of the groups of algae, nearly aU ofwhich live in salt water and have the characteristic color ; but a fewlive in fresh water. 297. Color. — Fresh specimens or those properly dried for theherbarium show the color which is characteristic of the great groupto which Nemalion belongs. Dried specimens of Irish moss(^Chondrus) and many other species furnish good illustrations. Thereare many variations of shade and intensity. Place a piece of a fresh or dried specimen of some species in
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