162 Pla?it Biology 



into cavities known as conceptacles (kon -sep' ta kl) (L. concipere, to 

 receive) . The latter bear the sex organs. In some species, male and fe- 

 male sex organs are located within the same conceptacle, while in others 

 the (male) antheridia (an the -rid' i a) (Gr. anthos, flower; idion, diminu- 

 tive) are borne on one plant and the {female) oogonia (oo-go'nia) 

 (Gr. oon, Q^g; gonos, begetting) are formed on another plant. 



Each oogonium, is borne on a short stalk and when mature contains 

 eight eggs. Numerous, m.ulticellular, branched, hairlike paraphyses (pa- 

 raf'ises) (Gr. para, beside; physis, growth) surround the oogonia. The 

 paraphyses bear enlarged antheridia, each of which produces numerous 

 pear-shaped sperms, each with two lateral, unequal flagella. The sperm 

 and egg unite in the water to form a zygote which forms a new Fucus 

 plant by cell division. Since the sperm is much smaller than the ^gg, 

 this process of fertilization is known as heterogamy (het er -og' a my) (Gr. 

 heteros, different; gamos, marriage or gamete). Fucus may reproduce 

 asexually by fragmentation. The cells of the plant body contain a double 

 (diploid) number of chromosomes, while the sex cells contain a single 

 (haploid) number. The gametophyte generation is reduced to merely 

 the male sperm or the female egg. Apparently the sperms are attracted 

 by a chemical substance secreted by the eggs. The sperms swim by the 

 action of the two unequal flagella. Unfertilized eggs may be induced to 

 develop by treatment with solutions of acetic or butyric acid, the phe- 

 nomenon being known as artificial parthenogenesis (par then o -jen' e sis) 

 Gr. parthenos, virgin; genesis, descent or birth) . 



RED ALGAE (PHYLUM RHODOPHYTA) 



These plants commonly are called sea "mosses" and contain plastids 

 with chlorophyll associated with a red pigment called phycoerythrin 

 (fai ko e -rith' rin) (Gr. phykos, alga or seaweed; erythros, red) and 

 sometimes with a blue pigment called phycocyanin. In most species the 

 plant is multicellular and may be branched or relatively simple, in the 

 form of a cylinder, ribbon, or sheet. Different species vary in size from 

 a few inches to several feet in length (Fig. 33). Each cell contains a 

 nucleus, central vacuoles, and one or several plastids, some of which 

 possess pyrenoids. Broad, conspicuous cytoplasmic strands which connect 

 adjacent cells are features of red algae. Stored food is an insoluble 

 "starch." Red algae are usually attached in warmer sea waters, with 

 a few species in fresh water. 



